Posts Tagged ‘pacific northwest’

A Star of The Cowlitz Cacophony

Monday, March 25th, 2013

The First Star Of The Cowlitz Cacophony…

 Luidia foliolata

 The winter in the Cowlitz Bay subtidal habitats is a time when nothing much appears to be happening, at least down to around a depth of 18m (60 ft) or so.   If large is bigger than a golf ball, then a lot of such large critters are visible; however, most of them, such as Pachycerianthus fimbriatus, the large cerianthid tube anemone, and the weathervane scallop, Patinopecten caurinus, while quite attractive and morphologically interesting, are sessile, and observing their behavioral array takes special skills or goals. 

A Weathervane scallop, Patinopecten caurinus, .  photographed in the ealry winter.

A Weathervane scallop, Patinopecten caurinus. photographed in the ealry winter.

 While both species do play noteworthy roles in the natural history drama of Cowlitz Bay, their version of a one dive’s act needs some serious augmentation to keep someone’s interest.  Individuals of neither species do much – at least overtly.  The anemone can … wait for it … retract down into its tube; … rapidly.  Wow!!  Golly gee, be still, my beating heart!  Woo… Woo… Impressive!!

Tube anemones or cerianthids are commonly found in Cowlitz Bay.  Here an individual of Pachycerianthus fimbriatus is blowing in the current at about 20 m.  The currents in this bay can common reach about 2km/hr

Tube anemones or cerianthids are commonly found in Cowlitz Bay. Here an individual of Pachycerianthus fimbriatus is blowing in the current at about 20 m. The currents in this bay can common reach about 2km/hr.  This individual was on the top of the relatively steep slope leading to much deeper water. 

These are the "mucus" and "ptychocysts" which are specialized nematocysts tubes which may extend into the sediment for a meter or more.  The animal can retract rapidly into them..

These tubes comprised of  “mucus” and “ptychocysts”, specialized nematocysts, may extend into the sediment for a meter or more. The animal can retract rapidly into them when startled.

And the scallop… well, now.  It may close its shells, an event truly worth a negative number on the excitement scale.  However, if one has been blessed by the fates, a scallop may actually swim (!) by rapidly clapping its valves together a few times.  This actually IS exciting.  Of course, probably the main reason for any excitement is that the behavior happens so rarely and it is compared to all of the other apparently non-interesting things happening in the vacinity.  Normally, Patinopecten scallops are the epitome of dull.  An individual spends its life in its little mud depression filtering water to obtain the phytoplankton it eats.  Of course, a fair-sized clam such as fully-grown weathervane scallop contains a large mass of delicious muscles along with other nutritious innards.  Consequently, the scallop is desirable prey item for any number of predators, including sea stars.  Presumably as a result, natural selection has given the scallop its rather spectacular swimming escape response.  If its mantle edge is contacted by a single tube foot from a sunflower sea star (Pycnopodia helianthoides), the scallop will usually start to clap its valves together rapidly and repeatedly, forcefully blowing water from between the closing valves forcing the clam up into the overlying water where it is blown away by the current.  In a way, calling this “swimming” is overstating the activity, it has no direction and a very limited extent.  However, currents in the area are often relatively strong, and the behavior can work to move the scallop away from the star.  And that is truly worth the show.  And then, after the scallop is done, it can be collected and become dinner for an altogether more lethal predator. 

 Normally, though, to see some interesting action in this habitat in the winter – and actually, through the rest of the year, as well – it is necessary to look for other predators at work.  Fortunately, the array of active predators on the surface, in the sediments and in the waters above the soft-sediment areas of Cowlitz Bay is rich, diverse, and impressive resulting in a lot of opportunities to see “ecology in action”.  The variety of predators ranges from diving ducks to dogfish and various other fishes from sculpins to flatfishes to sepiolid squids, nudibranchs, moon snails, and crabs.  However, perhaps the most commonly seen, abundant, and continuously active predators in the region are sea stars. 

 The most commonly seen stars are Pycnopodia helianthoides, the sunflower star, and Luidia foliolata, the snakeskin star, both of which may attain large sizes.  Sunflower star individuals have reportedly been measured at 1.5 m (5 feet) in diameter, while I have measured the average size in some Vancouver Island populations to be about 81 cm (32 inches) in diameter.   While Luidia foliolata individuals don’t commonly exceed 1 m (39 inches), they are often around 80 cm (31.5 inches) in diameter.  Pycnopodia helianthoides has been the object of a lot research, undoubtedly because of their large size and ubiquitous nature.  They are probably the most frequently encountered, relatively large, subtidal sea star in the region, and given the demonstrated importance of asteroids in ecologically controlling marine communities, they justifiably have attracted a lot of interest.  Luidia foliolata, hasn’t been investigated anywhere nearly as much, and as I spent more than a bit of time watching Cowlitz Bay’s L. foliolata, I thought this post would be a good place to introduce them.

 The Mouth That Roared, Wetly

 Asteroids are one of the most common educational poster children for invertebrates.  Back in those ancient days when I was in high school, some time in a biology class was spent dissecting and examining a poor, rather pathetic, pickled Asterias individual shipped in from the New England coast to Montana where it spent the last of its cohesive existence boring some kids who had never seen a body of water much larger than a small farm pond and who didn’t really care for any animals without fur, fins or feathers.  For those few of us who had a bit more on the ball (or so we thought), the asteroid’s pentaradiality along with its implied strangeness was really a pretty good introduction to invertebrate weirdness. 

 To even the most literate of us, a sea star was a pretty exotic critter; most of us had never seen a living one.  Had the specimen been remotely like a living animal, it really would have been a neat thing to examine, I think.  Unfortunately, the specimens reeked of formalin, and had a semi-slushy consistency resulting from much of the ossicular skeleton having dissolved in the acidic formaldehyde solution in which they had been stored.  Finally, to top everything else off, their normal purplish color had turned to a gawd-awful pale diarrhea brown.  Although the dissection wasn’t too hard, determining one tan glob from another was uninspiring to say the least.  Still… the effort was made to show us sea stars, and point out some pertinent typical features of their anatomy and biology, such as their complete gut, part of which, the so-called “cardiac stomach” could be extended into the clams that they ate, and the suckered tube feet which used suction to hang on to anything.  

 Long years later, I was trying to teach many of the same things to my students.  Fortunately, we were using specimens more freshly murdered “for the cause”, which weren’t a pasty mess.  I hoped the students were able to more carefully examine and “understand” what they were seeing in their specimens than I had been in mine so many years before.  Remembering my travails, I tried a number of different ways to make the important points.  One of these was that they got to examine other sea stars, to become aware of a bit of the diversity in this awesome group.  I always tried to have a live Luidia foliolata available in this exercise, as this was the first of a number of examples I used in my survey course to show the students that the “typical” animals they were learning about were, perhaps, not that “typical” after all.

Luidia foliolata

This specimen of the snakeskin sea star, Luidia foliolata was about 50 cm across the arms.

This close-up image, of the Luidia shown above, shows a patch of green (arrow) due to the presence of a species of endoparasitic green alga.  These infections are certainly lethal in some stars, but the outcome of such an infection is unknown in this species.

This close-up image, of the Luidia shown above, shows a patch of green (arrow) due to the presence of a species of endoparasitic green alga. These infections are certainly lethal in some stars, but the outcome of such an infection is unknown in this species.

To a careful observer, even one unfamiliar with sea stars, Luidia specimens are a bit weird.  When first observed, there is just something about them that seems “odd”; perhaps it is the spines on edges of the rays, or the odd “scale-like” pattern of plates on the top of the arms, or the non-descript brownish-grey color of the aboral surface, but they leave the impression that they are somehow “different”.   And, of course, they are (otherwise the “wily” instructor, aka “the old fart”, would not have put it out for them to examine). 

 Close examination shows that these animals lack the “suckers” or, more correctly, the “adhesive pads”, on their tube feet.  Nonetheless, they are still able to stick to surfaces and hang on to prey.  As is now known, sea stars attach themselves to substrata by a duo-gland adhesive system, not suction.  Duo-gland adhesive systems were first discovered using Luidia, in part because the stars were seen crawling up the sides of aquaria by some students who flashed on the fact that this is a star that lacks “suckers” on its tube feet, and it shouldn’t be able to climb up a vertical aquarium wall.  And if that weren’t odd enough, Luidia do not have a complete gut and do not (actually, cannot) extend their stomach into any clams that they eat.  In Cowlitz bay their primary prey are sea cucumbers, although small clams are also on the menu.  And all of the prey items are ingested.

A Luidia individual burying as it is feeding.  This image was taken in Cowlitz Bay in mid May.

A Luidia individual about 60 cm in diameter is  burying as it is feeding. This image was taken in Cowlitz Bay in mid May.

 Individuals of Luidia foliolata move over the substrate in Cowlitz Bay at a fairly good pace.  Although a big one can move along at about a meter per minute when it is, for some reason, in a hurry, normally their pace is more leisurely.   When they decide to feed, they stop, and start to burrow into the substrate.  The tube feet move sediments from beneath the arms and central disk out to beside the animal and the whole critter just slowly descends into the substrate, taking a day or so to disappear completely.  This activity leaves a large Luidia-sized star-shaped pattern on the sediment surface.   Presumably, as it descends, any potential prey items, such as individuals of sea cucumbers in the genus Pentamera, or small bivalves such as Macoma carlottensis are transported to the mouth and ingested.  I suspect they stop descending into the sediments when the tube feet have not encountered sufficient numbers of appropriate sea cucumbers for a while.  They spend some time, probably no more than a couple of days below the surface, feeding and digesting their meal.  When they are done, they rise up, emerge from the sand, regurgitate the indigestible remains of their meal, and mosey off looking for another place to feed.

 

This is depression left after the departure of a Luidia foliolata that had been feeding.  Some of the regurgitated indigestible remains of its meal are in the center area, the remainder were probably scavenged by some other animal such a large hermit crab.

This is depression left after the departure of a Luidia foliolata that had been feeding.  Some of the regurgitated indigestible remains of its meal are in the center area, the remainder were probably scavenged by some other animal such a large hermit crab.

 In Cowlitz Bay, the aboral surface of Luidia foliolata individuals is sometimes covered with a layer of the large caprellid amphipods, Caprella gracilior.  More than several hundred may be found on the back of a large star.  When the star buries in the sediment, these amphipods will be seen filling the star‑shaped pattern with a layer of pink skeleton shrimp.  The amphipods remain in place and when the asteroid rises from the sediments, they climb on their host and continue their ride.  What these are doing on the back of the asteroid is unclear.  This relationship has not been commonly reported, and I have never seen it elsewhere, although it was fairly commonly seen on my dives in Cowlitz Bay.  It was just one more thing about this place that made it a worthwhile place to work.

 

Caprella gracilior on Luidia foliolata.

Caprella gracilior on Luidia foliolata.

Caprellids waiting on the sediment for their submerged sea star to emerge.

Caprellids waiting on the sediment for their submerged sea star to emerge.

 

A mass of Caprella gracilior on the substrate over a buried Luidia foliolata.

A mass of Caprella gracilior on the substrate over a buried Luidia foliolata.

 The tale of Cowlitz Bay will continue in the future…

 Until later,

 Cheers,  Ron  

,

Benthic Natural History In Cowlitz Bay, Waldron Island.

Monday, February 4th, 2013

Passing into deeper water from the eelgrass beds found in the shallow nearshore environments of many embayments of the American San Juan Islands, the highly organic muddy sand substrate is typically replaced by a less organic or “cleaner” mixture of sand and silt.  Such a transition is certainly the case in Cowlitz Bay of Waldron Island.  I can verify that the silty-sand substrate continues to, at least, a depth of 50 m (165 feet).   Except for emergent rocky outcrops, this habitat type is likely characteristic of all the deeper water of Cowlitz Bay and the nearby San Juan Channel and Boundary Passages.

The tidal ranges that distinguish this region, coupled with its geography, mean that high tidal currents are the norm, and the volume of tidal water movement is immense.  All of this, added to the dense, rich plankton found in those waters creates a habitat that is probably nearly optimal for suspension feeders.  As a result, virtually all of the hard subtidal real estate is occupied some sort of organism specialized to grab food or nutrients from the water moving past them.  Subtidal rocky substrates are often characterized by dense populations of suspension-feeding epifaunal sea cucumbers.  And, although it may seem unlikely, some of the unconsolidated, silty-sand, habitats are also dominated by dendrochirote holothurians, albeit in this case these cases they are infaunal, not epifaunal.  Infaunal sea cucumbers dominate the subtidal Cowlitz Bay benthic environment below 10 m.    

0 - Pentamera cf populifera 11vii77 6m Cowlitz Bay, Waldron Id. 01 Juveniles

Pentamera individuals extending from the bottom of Cowlitz Bay, 11 July, 1977.  The abundance of the adult animals exceeds 20,000/m2 (about 0.2 m2) is visible.

Pentamera sp. indivdiual with some of the many juveniles in the sediment circled.  Taken 11 July, 1977.

Pentamera sp. adult indivdiual with some of the many juveniles in the sediment circled. Taken 11 July, 1977.  The juveniles become evident in the sediments in early summer, indicating spawning likely occurs in the spring.

Although a few other species are rarely found, the vast majority of these suspension-feeding, infaunal cukes belong to a few species of Pentamera.  The individuals belonging to the different species are relatively similar in size, shape, and coloration making them effectively indistinguishable in the field by non-specialists, so I will refer to them all as Pentamera.  Living buried in the sediments they feed by extending a small portion of the oral end of the body above the sediments.  This exposes just a bit of the animal, primarily the mouth, and its surrounding crown of highly-branched feeding tentacles.   

White, and only about 2 or 3 cm long, these relatively small sea cucumbers are often found in beds so very dense that in the summer, the benthic sediment appears snow-covered due to the many tentacles visible.  In the clear water of the late autumn and winter plankton-free periods, these holothuroids do not feed.  Presumably quiescent, they remain buried under the sediment surface.  During these seasons, the habitat looks relatively barren; with only scattered larger animals, such as individuals of tube anemones, Pachycerianthus fimbriatus, orange sea pens, Ptilosarcus gurneyi, snake-skin stars, Luidia foliolata, sunflower stars, Pycnopodia helianthoides, or weather-vane scallops, Patinopecten caurinus being evident to the casual observer. 

Patinopecten caurinus, the Weather Vane Scallop, about 15 cm (6" in) in diameter. Photographed in the Summer (June, 1977).  Note the visible Pentamera cukes.

Patinopecten caurinus, the Weather Vane Scallop, about 15 cm (6″ in) in diameter. Photographed in the Summer (June, 1977) on the benthic subtrate of Cowlitz Bay; note the abundant Pentamera cukes.

Patinopecten caurinus.  Area as before, except it was photographed in the ealry winter (December, 1976).  Note the lack of visible cukes.

Patinopecten caurinus. Area as before, except it was photographed in the ealry winter (December, 1976). Note the lack of visible cukes.

With beginning of the diatom bloom starting in February, smaller life “returns to”, or more correctly, becomes evident again on the benthos.  The sediment becomes covered completely with a thick and rather ugly, dense dark brown film, consisting of several species of microalgae, primarily diatoms and dinoflagellates. 

Unidentified Polyclad Turbellarian, photographed in April, 1983.  The "black material" is the diatom film that is found in this area in the spring.

Unidentified Polyclad Turbellarian, anterior end to the left, photographed on April, 1983 on the substrate in Cowlitz Bay.  The “black material” is the diatom film that is found in this area in the spring.

By early March, many turbellarian flatworms of several visually distinctive types are commonly found gliding over the brown algal film and sediments.  These small worms, each only a few millimeters long, may be distinguished by their differing shapes and color patterns.  Although common, at least in the spring, virtually nothing is known of their natural history.  Shortly after the worms become common, small caprellid amphipods, otherwise known as “skeleton shrimp”, seem to appear out of nowhere and are soon found covering the diatom film.  These small, about a centimeter (0.4 inch) long, animals reproduce rapidly and soon reach abundances around 1 animal per square centimeter, or a density of 10,000 animals per square meter.  As they become common, pelagic predators, such as ctenophores and chaetognaths, may be observed grabbing copepods off the bottom and swimming back up into the overlying water.

A Sagitta (planktonic chaetognath carnivore) photograph near the bottom, hunting for caprellids.

A Sagitta (an almost completely transparent planktonic chaetognath and a predator normally on zooplankton) photographed near the bottom, where I have seen other individuals grab caprellids.

 By the middle of March, the spring plankton are in full bloom and the Pentamera are beginning to feed.  By moving up and down in the sediment, the resulting bioturbation soon destroys the diatom film, and the sediment becomes relatively clean again.  Snake-skin stars, Luidia foliolata, are common in this habitat where these sea cucumbers are their principal prey.  Caprellid amphipods, Caprella gracilior, and small hermit crabs are often seen on the aboral surface of the stars.  The Luidia-sized, star‑shaped, feeding depressions, along with the small piles of regurgitated remains attest to the star’s feeding habits.  Pycnopodia helianthoides is also commonly found in these beds and may also feed on the sea cucumbers.  Some aspects of the natural history of Luidia in this habitat will be discussed in subsequent post.

 Individuals of the large, up to 15 cm (6 inches) in diameter, weathervane scallops, Patinopecten caurinus, rather rare elsewhere in the San Juans, are found not uncommonly in these cucumber beds.  They are found lying in shallow, somewhat bowl-shaped, depressions probably created over time by the scallops’ feeding currents which might gently displace and excavate the sediments.  Eaten by the sunflower star, the scallops will swim in response to being touched by the predator.  They are not particularly vigorous swimmers, however, nor do they seem to start swimming immediately, thus they could be captured relatively easily.  Their shells are a common feature in this habitat, so presumably some predators are capturing them.  These large shells, either living or dead, provide about the only hard substrate in these habitats, and are often covered with barnacles, algae, or occasionally attached bryozoans or hydroids. 

Maroon more pachycerianthis

Both color varieties or “morphs” of  Pachycerianthus fimbriatus found in the benthos of Cowlitz Bay.

The tube-dwelling anemone, Pachycerianthus fimbriatus, is particularly common in this habitat, and becomes very abundant just below the dense Pentamera beds in the more silty habitats of the steeply sloping areas.  Pachycerianthus individuals may be colored either gray or a dark brown to maroon.  These do not appear to represent separate species, and the different colors have no known significance.  Close examination of the anemones will show some very small epifaunal, possibly stenothoid, amphipods visible as small dots moving over the anemone’s body and tentacles.  During the spring and early summer periods of dense plankton, it is possible to watch the Pachycerianthus catch copepods, and other small crustacean zooplankton, with their long tapering, thin, tentacles. 

An ectoparasitic or commensal stenothoid amphipod on a Pachycerianthus tentacle.  Assuming the tentacles are about the same size (and they are) compare this amphipod to the hyperiid amphipod captured as food by a different tube anemone (next illustration).

An ectoparasitic, or commensal, stenothoid amphipod on a Pachycerianthus tentacle.  Assuming the tentacles are about the same size (and they are) compare this amphipod’s size to that of the hyperiid amphipod captured as food by a different tube anemone (next illustration).

A small Pachycerianthus fimbriatus with a captured planktonic hyperiid amphipod (arrow).

A small Pachycerianthus fimbriatus with a captured planktonic hyperiid amphipod (arrow).

 These slightly deeper habitats where Pachycerianthus is most common, ranging downward from about 10m (33 feet) in depth, have a silty sand substrate.  Pentamera are found in these regions, they are just not as abundant as they are in the dense assemblages in shallower water.  Individuals of the orange sea pen, Ptilosarcus gurneyi, are well represented in these deeper habitats, and although they are not as abundant here as they are in the dense sea pen beds of the lower Puget Sound region, they are nonetheless found relatively frequently.  Occasionally, a different type of pennatulacean, a sea whip, may be found.  In the genus Virgularia, these whips are narrow pennatulaceans, with short “leaves”.   At least two species within this genus found in our waters and they are not terribly difficult to distinguish in the field.  The species found in Cowlitz bay is small, tan to whitish, with small “leaves” and is seldom over 15 cm (6 inches) in height.  The feeding zooids often appear to arise from directly from the central stalk.   The other species, found in other areas, such as Lopez Sound, is larger and more robust, pink to orange, and often reaches heights of 50 or more centimeters.  This species has larger relatively distinct “leaves” with the gastrozooids on them. 

A small, about 8 cm (3.5 in) high, pennatulacean, probably a species of Virgularia.

A small, about 8 cm (3.5 in) high, pennatulacean, probably a species of Virgularia.

 Several nudibranch species are also found in these areas, most of which are probably preying on the cnidarians.  The largest and most evident of these are individuals of Dendronotus iris.  These are amongst the largest local snails; in this area they often reach lengths exceeding 25 cm (10 inches) which is probably due to the high abundances of their preferred prey, the Pachycerianthus anemones.  They approach the anemones by slowly crawling under the tentacle crown, to where the anemones extend from their tube.  They, then, reach up rapidly, bite, and hang on to either a mass of tentacles or even the anemone’s column.  Generally, the Pachycerianthus rapidly withdraws into its tube when it is bitten, and in these cases, it often pulls the predator in with it.  Sometime later, the Dendronotus iris often crawls out of the now empty tube, and may set off in search of another anemone.  The nudibranch may, at times, lay its loosely coiled egg masses attached to the Pachycerianthus tube, bits of shell, or just bits of the sediment.

0 - Dendronotus iris Cowlitz Bay, Waldron Id. -7m 11vii77 WA 01

A 10 cm (4 inch) long Dendronotus iris in Cowlitz Bay. Photographed at a depth about 7 m. This large nudibranch reaches over 30 cm (12 inches) in length, and eats Pachycerianthus. 

Other nudibranch specimens are found in the area, and they can be relatively common at certain times of the year.  Dendronotus albus specimens will be found occasionally, preying on those few hydroids that are found attached to the shell fragments or other hard substrata present on the sediment surface.  These nudibranchs are slender and may reach lengths of about 10 cm.  The basic ground color is white, but the tips of the branched cerata are tipped in orange.  Individuals of another dendronotid, Dendronotus albopunctatus, are often abundant in the spring.  These animals are brown to pink and freckled with small light dots.  They only reaches lengths of 2 to 3 cm (up to about 1.5 inches), but they are recognizable by their somewhat “oversized”, relatively large, “front” cerata, which are often about a centimeter in length.  Little is known of the natural history of this species, although it is likely a predator on small cnidarians.

Dendronotus albus.

Dendronotus albus is a not uncommon, small, about 3 cm, (1.2 inches) long, nudibranch in habitats such as those found in Cowlitz Bay.  It eats hydroids, as this individual was doing when photographed

0 - Dendronotus albopunctatus Cowlitz Bay, Waldron Id. -9m 28iv83 WA 01

Dendronotus albopunctatus, about 3 cm (1.2 inches) long on the sediment of Cowlitz Bay.  It also has been seen to eat hydroids.

0 - Acanthodoris brunnea, Cowlitz Bay, Waldron Id.,  -9m, 13v86  WA 01

Acanthodoris brunnea, about 2 cm (0.8 inch) long, photographed on the sediment of Cowlitz Bay.  Reported to eat bryozoans, this dorid species is found on muddy-sand, a habitat notably lacking in bryozoans.  In this region and habitat, it is likely eating something other than bryozans.

Acanthodoris brunnea is another nudibranch species that is somewhat common at times in this habitat; little is known of its natural history.  These animals are small dorids, roughly the same size as Dentdronotus albopunctatus, reaching lengths of 2 to 3 cm (up to about 1.5 inches).  Their basic coloration is brown; the individuals are covered with distinctive relatively large papillae on the back.   This species is considered to be predatory on bryozoans, but that is unlikely in this region as bryozoans are exceedingly rare in this habitat.

Also found in these areas are pennatulid-eating nudibranchs in the genus Tritonia.  The most abundant of these are individuals of the small white Tritonia festiva, described in the earlier post on sea pen beds.  Here, as well, T. festiva individuals seem to prey on Ptilosarcus.  Individuals of the larger, orange nudibranch, Tritonia diomedea, are also occasionally seen in these areas.  They seem to prefer the larger Virgularia as prey.  

Large shelled gastropods are relatively rare in this particular habitat, although several smaller species can be very abundant.  Perhaps the largest commonly found gastropod, and certainly one of the most beautiful, is the wentletrap,  Epitonium indianorum.  These animals are often found buried near to the bases of the tube anemones upon which they feed.  As with most snails, wentletraps have a feeding organ called a radula; unlike the “classic” gastropodan radula which functions something like a rasp, filing off pieces of tissue, the wentletraps’ radulae are highly modified and look like an inverted thimble lined on the inside with sharp teeth.   A wentletrap crawls up to the anemone and pokes the anemone with its radula everting the “thimble” in the process.  This turns the radula inside out, which in turn, carves a circular hole in the tissues on the side of the anemone.   The lacerated tissues are eaten, and the snail extends its proboscis which has the radula on its tip through the hole and proceeds to use the radula to cut up and eat other internal anemone tissues.  These snails reach lengths of 3 cm or more, and don’t seem to move much once they have found an anemone to feed on.  It is recognized by the distinct axial ribs, the rounded aperture, and the relatively high spire.

 One cephalopod can be relatively common in the lower slope areas, the Pacific Bob‑Tailed Squid, Rossia pacifica.  This small benthic squid lives buried in the bottom during the day.  If a diver is careful, they can sometimes see the slight depression that the Rossia occupies, and then can make out the eyes watching him.  The hole for the siphon is generally visible and if approached carefully, one can see the regular breathing movements of the mantle.  Rossia pacifica reaches lengths of about 10 cm, and seems to live about a year or eighteen months.  They have an interesting, stereotyped, escape response which I have described, briefly, in a previous post.  This small squid preys on small shrimps, crabs, and fishes, and is a nocturnal hunter.

Well, that’s enough for now… :-)

More later,

Cheers, Ron

 

 

 

 

 

19 January, 2013 — Spermcasting

Saturday, January 19th, 2013

Hi Folks,

The news of some days, of course, is better than on others. And the news of the January 16, 2013, was grand! It contained a term I had never seen, but one I will be sure to use whenever possible, “spermcasting”.  I have to admit, when I first read it, it conjured up visions of fly casting, but with some essential differences; such as the type of rod one uses…  Aaah…  But, let’s not go any further down that road. :-)

As the authors of the term meant it, in its basic form spermcasting would be seen in broadcast spawning animals such as many sessile marine invertebrates, and it would presumably have a feminine complement of ovacasting. In other words, “spermcasting” is the release of male gametes into the surrounding water as a means of reproduction. This type of reproduction is also seen in mobile animals such as echinodermsBroadcast spawning animals typically have simple reproductive systems, without any externally visible modifications.  The gametes are made and simply released through a “gonopore” into “the great outside world”.

A male sunflower star Pycnopodia helianthoides photographed  "spermcasting" otherwise known as "broadcast spawning" in Northern Puget Sound.

A male sunflower star Pycnopodia helianthoides photographed “spermcasting” otherwise known as “broadcast spawning” in Northern Puget Sound.

 

A close up of the animal in the previous image showing the sperm suspension being released from the gonopores.

A close up of the animal in the previous image showing the sperm suspension being released from the gonopores.

However, spermcasting is something that is not generally considered to be part of the reproductive behavior of animals with a penis. In fact, over the array of invertebrate animals, the variety of penises, receptacles, openings, and the behaviors to get them all together is truly amazing, but spermcasting has not been considered a part of that behavior.  And why should it?   Because a penis is used to place sperm in some sort of receptacle or opening in a female, spermcasting has been thought to be unnecessary.   

While obviously commonly occurring, the actual physical act of the male’s transferring sperm to the inside of a female’s genital tract, “copulation”, is actually seldom observed in marine animals.  The reason for this is obvious.  For many species where reproduction involves internal fertilization or union of their gametes, reproduction may be an intrinsically hazardous process; and its duration and frequency is often minimized.  Often, copulation involves the intimate meeting of two animals that may be predatory and dangerous to one another. The terrestrial examples of the preying mantis or spiders such as the Black Widow come to mind, but the marine environment also has its share of dangerous liaisons. In such animals copulation often requires all sorts of behavior to ensure that the predatory behavior of both parties is “defused”. Some of the best known examples of such behavior occur in octopuses.

A large individual of the Giant Pacific Octopus, Enteroctopus dofleini.   Highly predatory and cannibalistic, and reaching weights well in excess of 50 kg (110 pounds), precopulatory behavior that may last several hours is necessary  before the animals can safely remain in each other's proximity for reproduction.

A large individual of the Giant Pacific Octopus, Enteroctopus dofleini. Highly predatory and cannibalistic, and reaching weights well in excess of 50 kg (110 pounds), precopulatory behavior that may last several hours is necessary before the animals can safely remain in each other’s proximity for reproduction.

 Copulation may place the animals at risk of predation by animals other than a potential mate. When animals are copulating, their attention cannot be on predator avoidance.  Consequently, natural selection has forced the development of behavior that reduces the risk of being seen – and eaten – such as nocturnal or reclusive mating. In some other animals, the act is over so fast, that the odds of an observer even noticing it range between slim and none. Pairs of one nudibranch species, Hermissenda crassicornis, can “do the deed” in a few seconds. And in those animals the act is reciprocal, the partners are hermaphrodites so each one gives and receives.  However, the process is seldom seen, or if it is, it is seldom recognized for what it is.

Hermissenda crassicornis, the so-called "opalescent nudibranch".  Individuals of this hermaphroditic species reciprocally exchange sperm in some of the fastest copulations known.

Hermissenda crassicornis, the so-called “opalescent nudibranch”. Individuals of this hermaphroditic species reciprocally exchange sperm in some of the fastest copulations known.

As a result, generally, people have inferred internal fertilization or copulation by the presence of a penis and the associated female plumbing. And some animals are legendary in their endowment. Some of the best known in this regard are barnacles whose penises are often able to extend several times the length of the animal. Barnacles don’t actually copulate, relatively few crustaceans do, but they use the penis to deposit sperm in the females’ mantle cavities, and sperm behavior or the female partner ensures the gametes find their ultimate destination. However as the saying goes, this “pseudo-copulation” is “good enough for government work”.  Barnacles are sessile, glued to the substrate by glands in their head, consequently, their reproductive success, and their “evolutionary fitness”, depends on how far they can reach out to touch someone with their legendary penises. Fortunately, as they are hermaphroditic, any neighbor will do.

Balanus nubilus, the giant "cloud" barnacle of the N. E. Pacific.  Large individuals reach up to about 15 cm (6 inches) wide at the base, and are often solitary or a relatively great distance from their neighbors.  Spermcasting would definitely benefit their reproduction.

Balanus nubilus, the giant “cloud” barnacle of the N. E. Pacific. Large individuals reach up to about 15 cm (6 inches) wide at the base, and are often solitary or a relatively great distance from their neighbors. Spermcasting would definitely benefit their reproduction.

The need for (pseudo-) copulation, inferred by the presence of a penis, in barnacles could present a significant limitation in their reproductive capability relative to broadcast spawning animals, and hence it could severely limit their evolutionary fitness. Nonetheless, as far as anybody knew, barnacles put their amazingly large “equipment” to good use, copulated, and “THAT” was “THAT”.

Except, as it turns out “THAT,” is not “THAT”.  In a paper published online on January 16, some scientists have shown, rather elegantly that at least one species of barnacles; the common gooseneck barnacle of the NE Pacific, Pollicipes polymerus, does things quite a bit differently. They spermcast…

They are apparently able to both throw caution to the winds – or their spermies to the seas – and, amazingly enough, have this result in successful fertilization. Using genetic markers and some elegant and careful work, the researchers, from Dr. A. Richard Palmer’s lab at the University of Alberta, have shown that spermcasting occurs commonly in the goose neck barnacle, and even occurs in animals that can reach a partner to mate in the “traditional” manner.

Such extraordinary findings really upset the traditional view of spawning and copulation. After all, if barnacles can spermcast… it certainly seems that other animals possessing normal copulatory organs may also be able to do this.  No longer is it possible to look at the anatomy of species wherein the males possess a penis, and blithely assume that they only reproduce by copulation. 

Of such uncertainty, good research is made, as people have to ascertain the mode of reproduction.

As the authors of this paper state in the abstract, “These observations (i) overturn over a century of beliefs about what barnacles can (or cannot) do in terms of sperm transfer, (ii) raise doubts about prior claims of self-fertilization in barnacles, (iii) raise interesting questions about the capacity for sperm capture in other species (particularly those with short penises), and (iv) show, we believe for the first time, that spermcast mating can occur in an aquatic arthropod.”

More later,

Cheers, Ron
 

A Pentamera-Dominated Sandy Environment

Wednesday, August 29th, 2012

The Place – Where, When, Why.

The American San Juan Islands in the Northern Puget Sound. Waldron Island is at the top (North), CB = Cowlitz Bay. The Friday Harbor Laboratories location is indicated by the colored star on San Juan Island.

Cowlitz Bay, Waldron Island, Washinton. Viewed from the north, July, 1976. The primary study area is indicated in blue, the rocky reef used for orientatioin is indicated in yellow.

Cowlitz Bay of Waldron Island, Washington initially attracted my attention in the early 1970s as the result of a collecting trip undertaken out of the University of Washington Friday Harbor Laboratories (FHL) as part of my doctoral dissertation research.  These trips used a converted fishing boat which was configured to pull a “biological dredge”, which is effectively a metal frame with some sort of netting attached to retain the catch.

M/V HYDAH
Operated under contract to the University of Washington’s Friday Harbor Laboratories, this was the boat I used for dredging in the 1970s. Photographed in San Juan Channel, July, 1976.

This dredge is lowered to the sea floor and pulled along it for some, supposedly, known distance.  Depending on vessel’s velocity, the configuration of the dredge frame, and the substrate,  the apparatus will – optimally – dig into the bottom and collect a sample of that bottom along with what is in it.  The dredge is returned to the surface, emptied on to a “sorting table”, typically, a large box-like apparatus which contains the sample.  The sample is rinsed and organisms of interest are collected.

Samples collected in this manner by oceanographic vessels using well-designed dredges can be taken in a reasonably precise manner.  For example, if the apparatus is pulled at a given speed, it will dig into the bottom of a certain type to a known depth.  Our samples were nowhere near as well-controlled!  In shallow waters, 60 to 200 feet, we could be reasonably sure of getting something.  At other times, it was quite feasible to have the dredge hang up on an underwater obstacle  no sample would be obtained.   Very occasionally the apparatus could be lost, along with all of the cable pulling it.  This latter proposition is, at the very least, expensive and, at least to the person in charge, embarrassing.  Consequently, one had to choose one’s dredging sites with care, and hope that the boat driver knew what he/she was doing.

To help pay for my studies, I applied for and was awarded what at the time was referred to as an National Science Foundation doctoral dissertation grant.  As part of the grant, I requested funding to explore habitats in the region for various of the turrid gastropods I was studying.  I used these funds to pay for dredging trips to the soft sediment habitats that nobody else was really interested in investigating.  I would sort through the materials obtained by the various dredges and if I found some of my “target” snails, and if the area seemed otherwise interesting and diveable, I would try to do some diving in the area and ascertain the habitat first hand.

I chose to dredge in Cowlitz Bay because it was off of the beaten track.  Most of the dredging trips out of the FHL went to the same places over and over, ignoring other areas both near and far from the labs.  As I could readily get information from the commonly dredged places, I decided to spend my grant’s money to go elsewhere.  I didn’t find much in the way of turrids in the dredging results from Cowlitz Bay, but I did find some live scaphopods, Rhabdus rectius, to be exact.

Scaphopods, 3 species commonly found in the Pacific Northwest. Gadila aberrans is not found in Cowlitz Bay, the sediment is unsuitable, and the salinity is likely too low.

As I had an abiding interest in scaphopods  predating my interest in turrids, I later spent some relatively intensive field work looking at the scaphopods and other critters found in the bay.  I did over 30 dives in Cowlitz Bay, most of them with my friend, Dr. F. Scott McEuen, as my diving partner.  Our objectives, on many of these dives, were doing various types of quantitative sampling, either doing transect surveys or collect samples for later laboratory analyses.  On other dives, we simply took pictures.  Scott was investigating the sea cucumbers in the genus Pentamera which are found there in absolutely mind-boggling numbers, and I was looking at the scaphopods whose abundances, while significantly less than boggling, were still high enough to make sampling worthwhile.  Additionally, there were a lot of other interesting things of one sort or another, either in the bottom, on the bottom, or swimming above the bottom of the bay that served to tweak our collective or individual fancies bringing us back to the bay time and time again.

Sea cucumbers in the genus Pentamera in the substate in 20 feet (6 m) of water in Cowlitz Bay in July, 1977. Juveniles of the year have just settled, but are too small to see in this image; all the cukes that are visible are adults. The cucumber population density is in excess of 50,000 animals per square meter.

The Place

This large west-facing embayment opens toward the west.  Most of my diving was done in the northern half of the bay.  There is an underwater ridge running more or less east-west located in the middle to eastern portion of the bay, about one third of the distance from the bluffs forming the southern edge of the bay to the spit of land forming the northern edge.  The ridge has a kelp bed growing from it, so to orient ourselves when we arrived, we would find the kelp bed and go north in our boat until we had covered about half the distance to the northern shore.  There we’d anchor, typically in about 60 feet (18 m) of water.  When we anchored we were a long way from any shoreline, easily a half mile (700 to 800 m), and on cold, drizzly, gray winter days, it seemed a lot further.  This meant that when we hit the bottom after following the anchor line down, we took careful compass bearings so that when we needed to surface we could find our way back to the vicinity of the boat.  Or at least that was the plan.

The substrate in the area was sand or sandy-mud and was generally gently sloping to the west or south.  The deepest we normally swam to was about 90 feet (27 m), and most of our dives were between 20 to 60 feet (6m to 18m). Occasionally, we did a dive in the shallower eastern reaches of the bay.  Over the course of several years, I made dives in this region in every season, and what I will discuss in this sequence of blog articles is a summary and compilation of my diving logs from all of the dives.

Near-shore shallow waters of the NE Pacific are tremendously influenced by the local climate.  The annual cycle is worth mentioning here, as I will discuss details of it in passing.  It is not too much of a stretch to say, “Everything depends on the weather”.  Undoubtedly, climate change is affecting the subtidal communities of this region; while I can guess some of the changes due to global alterations, I don’t think that is a profitable course of action.  These images were taken in the period from about 1976 through 1986, and I will use the observations I made at the time

The Seasons

The seasons of the marine shallow subtidal habitats in this part of the Pacific Northwest region, basically the shallow waters of  Northern Washington, British Columbia, and Southeastern Alaska, bear only a passing resemblance to the seasons likely to be encountered above the waterline (Table 1).  As with the terrestrial environment, the primary driver of seasonality is sunlight, but sunlight’s effects come in pure and modified forms.  Pure solar illumination is really pretty uncommon in this region, and typically is found mostly in the summer; generally these bursts of sunlight result in phytoplankton blooms that degrade visibility significantly.  The blooms tend to alternate, in  textbook fashion, with periods of very clear water, probably due to zooplankton blooms.  When we were diving in this area, the visibility we would expect was predictable most of the year, but in the later summer, as the old carnie saying goes, “You pays your money and you takes your chances.”

The rest of the time, sunlight is filtered and muted through clouds.  While solar illumination is, of course, the ultimate driver for the region’s weather both illumination and weather events working together results in the overall marine environment of the entire region exhibiting remarkably stable physical conditions.  Temperature variations below 16.5 feet (5 m) are minor, seldom varying by more than a couple of Celsius degrees, and generally no more than about 6 or 7 Fahrenheit degrees.  Salinity fluctuates much more drastically due to the rainfall and runoff from snowmelt, but even so, deeper areas, below 10 m (33 feet) remain reasonably stable.  Freshwater layers due to major runoff events such as floods tend to flow out over the more stable underlying areas.  This is not to say there are no effects due to these factors, but major salinity and temperature effects are abnormal, variable in extent and degree, and relatively unpredictable.

Table 1.  Subtidal Seasons Of Cowlitz Bay,

And

The Northern San Juan Islands, Washington. 

Season

Starts

Ends

Cause

Manifestation

Dark

Mid-October

Mid-February

Low Illumination, Cool Temperatures

“Everything is shut down”

Clear water, no plankton

Diatom

Mid-February

Early-March

Increasing illumination and temperature, Nutrients from spriing runoff increase

Substrate becomes covered with a thick diatom coat.

There is clear water with scarce plankton.

Filter-feeders start emergence

First Plankton

Early-March

Late-March

As Above

Phytoplankton blooms;

Water becomes greenish and visibility drops;

Substrate diatom layer becomes thinner;

Some benthic herbivores present; 

Filter-feeders emerged.

Second Plankton

Late-March

Late – May

As Above

Zooplankton bloom becomes noticeable;

Phytoplankton presence is less, Water visibility increases slightly,

Water color changes from green to gray-green/aquamarine;

Spawning is occurring with some benthos,

Diatom cover is largely gone,

Benthic herbivores are common.

Settlement

Late – May

August

Nutrients from runoff become less, Illumination and temperature still increasing

Small animals and settled juveniles become very common. 

Plankton pulses, going from phytoplankton dominated to zooplankton dominated to no plankton (clear water) in short (week long) sequences; 

Water often cloudy, greenish white.

Growth

August

Early- October

Runoff absent,  Illumination begins to drop, Temperature peaks.

Filter-feeders evident;

Benthic predators very active. 

Diatom cover almost gone. 

Small predators disappearing.

Shutdown

Early October

Mid to LateOctober

Temperature drops, Illumination drops, Rains begin.

Plankton disappears;

Filter-feeders shut down. 

Water clears up, becomes dark green.

Diatoms on benthos gone.

 
 
 
 
 

The Current Conditions Are….

Cowlitz Bay, as in the rest of the San Juan Islands, has semidiurnal tides which generally have a pattern of two unequal high tides interspersed with two unequal low tides.   The tidal cycle is primarily driven by the lunar cycle, and the relative magnitudes of the highs and lows fluctuate through the year following the lunar calendar.   The most extreme tides, the largest difference between the higher high and the lower low tides, are found near the solstices, while the least extreme tides are found near the equinoxes.   The differences between the most extreme tides is reflected in the  velocity of water currents, and the unconsolidated substrate in the bay belies the rather strong currents that may occur there.

Coming up next… the animals and interactions.

 

Ecological Observations From Northeastern Pacific Subtidal Habitats – Sticky Post #3.

Friday, August 24th, 2012

Series Introduction.

All things must have a beginning, and putting these brief words prior to the beginning of my “series” about my subtidal ecological/natural history observations and “reflections”, is probably as good a place as any to put them.  I hope to add to these tales from time to time, and I hope “the times to times” are more frequent than they have been previously in my blog.

Exiting the water on the south shore of Alki Point in Seattle, Washington.

Here I am exiting the water on the south shore of Alki Point in Seattle, Washington in October, 1982, after doing a dive examining the sea pea bed that was found offshore of that beach (R. Fredrickson image).

That is the plan at least.

If I can do it, I hope to add in this series many of my unpublished and, prossibly, unpublishable, observations made while diving over the period when I was actively doing subtidal natural history research; roughly the period from 1971 to 1993.  There are a lot of reasons for writing this now, but suffice it to say, I am definitely not getting younger and it is possible that some of this material may be of interest to a few other people.  At the very least, they, and the rest of the readership, should get a good laugh out of considering that I would think that it could be useful. :-)

Nonetheless, I think it would be nice, if it simply did not disappear with my demise.  Perhaps, as well, what I write here will serve as an historical record of what occurred prior to any future wholesale habitat destruction due to climate change or some more directly local human activity.   Of course, the fact that many of the presumed untouched Puget Sound and Pacific NW subtidal habitats had previously been messed up seems to have escaped the notice of many people, researchers and divers alike, working in the region.  I will try to point out some of these communities when the need arises.

On the other hand, maybe all I am doing, however,  is just putting down the garbled memories of an old man.  I guess you get to choose.

I will add these tales, or studies (depending on how seriously one wishes to take them), in no particular order over no particular time frame.  Rather I will add them as my muse allows.  Those readers who have previously read my ramblings will realize I know how fully well that my writing depends upon my personal muse  and how she feels about each topic I try to write about.  If she doesn’t like it… nothing good will be written.  If she loves it… well, maybe the writting will still contain nothing good, but if so, there will be a lot of it!  When she likes the topic, though, my good gawd, how the writing flows.  The gorgeous litle blue-green minx (= my muse)  has been known to change her mind in the middle of an article as well.   That has NOT been a fun experience, but it occurs.  As I am writing here to just enjoy the process, I think she will be the helpful creature she truly can be.

If anybody that reads these pages is a scientist, I will add the advice of “not to hold your breath waiting for any of this to appear in the peer-reviewed journals”.  Trying to publish most natural history information and observations in such venues is a serious waste of time and effort.  And if you have gotten this far, you have read the first paragraph and realize that I feel don’t have that much time to waste.   So…  On with the show!

To examine these posts/articles/essays in this “series” as a group:

Please click on the blog “Category” (listed at the top of the column to the right) titled:

 

“Ecological Observations From Northeastern Pacific Subtidal Habitats”.

 

 

To Pen A Tale Of Pens…

Wednesday, September 28th, 2011

Life History

The term “life history” is really a misnomer.  What the term really means is the generalized “story” of an average individual’s life.  Probably the animal whose life history is best known is the human.  Broken down by geographical region, and other demographics, it is possible to predict with surprising accuracy the life span, as well as the major life experiences, such as the number of offspring, and when they occur, for the average individual of many human populations.  In the case of humans, the driving force for the accumulation of such knowledge is not the desire for “abstract knowledge,” but rather the desire to make a profit.  On such knowledge is the insurance industry built, and it is based to a great extent on studies of human life history profiles extended to the greatest precision possible.  We also know the life histories of a large number of other, mostly terrestrial, organisms.  In these cases, biologists have spent a great deal of time studying populations of these animals and have noted when the animals are born, when they die, how long they live, when they mate, and so on.  All of these data can be massaged and manipulated statistically to provide a good understanding of the essential experiences of an average member of those species.

However, once we pass out of the terrestrial realm and into the oceanic environment, our ability to see all of the relevant aspects of any given organism’s life is significantly obscured by a wall of water.  To accumulate the data and the observational knowledge to flesh out a “life history” takes good, down to earth (or ocean bottom), tedious, long-term, expensive and dedicated research.  Because of the effort involved, such work has been completed for precious few animals, most of which are temperate, due primarily to the prevalence of marine laboratories in temperate regions.

The Story

In this essay, I summarize the results of a series of research projects concerning a temperate octocoral, the sea pen, Ptilosarcus gurneyi.   This species has also been known as Ptilosarcus quadrangulare,  Leioptilus quadrangulare, Leioptilus guerneyi, and  Ptilosarcus quadrangularis, but these names have long been considered to be junior synonyms.  Nonetheless, they still turn up from time to time, particularly in comments on the internet.  The basic research on which this article is based was reported in two papers (Chia and Crawford, 1973; Birkeland, 1974), but in addition, there is a significant amount of my own hitherto unpublished research.  For ease of readability, I will not cite either main reference again.  If the reader is interested in more detail, please read these articles or contact me directly.  In total, this information represents several thousand person-hours of observational time.  As far as I know, no similar body of knowledge exists for any tropical octocoral, although there are similar accumulations of information regarding some Mediterranean gorgonians.  I hope, however, that this example will give some appreciation for the life history of, at least, one type of octocoral.  Perhaps, as well, this essay will present the types of data needed to discuss the biology of these animals.

Figure 1.  A mature Ptilosarcus gurneyi individual extended about 50 cm out of the sediment.  The primary polyp consists of the base which extends into the sediment, and the rachis or stalk extending from the base up between the “leaves.”  The gastrozooids or feeding polyps are found on the outside of the leaf edges, while the siphonozooids, or pumping individuals, are found in the orange regions on the sides of the rachis.  The “warts” on a few of the leaves are caused by a parasitic isopod living inside the pen’s tissues.

 

Figure 2.  A portion of a sea pen bed in the central Puget Sound region, the depth was about 15 m.  Water flow was from the left, and the foreground field of view is about 1.5 meters (5 feet) across.

Sea pens are octocorals.  Taxonomically, they are placed in the Order Pennatulacea of the Subclass Octocorallia (= Alcyonaria), in the Class Anthozoa of the Phylum Cnidaria.  All of this jargon means they are animals whose major body parts consist of modified polyps.  Being octocorallians, their polyps show an octamerous or eight-fold symmetry most obviously manifested by the presence of eight tentacles around the mouth of the feeding polyps, or gastrozooids.  These eight tentacles each have a series of small side branches, a condition referred to as “pinnate branching.”  Unlike other octocorals, sea pens are mobile.  While they are sessile, living in unconsolidated ocean bottom sediments, they are not fastened to the substrate and at least some sea pens are capable of significant locomotion.

The adult sea pen is body considered to be comprised by the fused modifications of three types of polyps.  The base and central stalk region, or rachis, is considered to be the modified original polyp.  The feeding polyps possess tentacles are called gastrozooids and typically found either extending from the surface of the rachis much like the spokes of an umbrella, or on lateral extensions from the rachis, the “leaves”.  Depending on the sea pen species and the adult size, there may be from about ten to many thousand gastrozooids.  Embedded in the rachis surface are the siphonozooids; modified polyps lacking tentacles.  These structures consist of a “mouth” which is lined with microscopically sized, beating, hair-like projections called “cilia.”  Siphonozooids pump water into the body of the colony.  The colony has quite an intricate system of channels which allow the movement of water and nutrients throughout the body.  The forces necessary for the water movement comes from muscular contraction of the body and the beating of the cilia lining the water channels.

Figure 3.  The “leaf” edges of a mature sea pen showing many gastrozooids.  The leaves are oriented into the current, and can generate hydrodynamic lift.  When the animals are disturbed, they may orient into the current, inflate, climb out of the sediment, and drift away in the current.

 Figure 4.  The siphonozooid region of a sea pen rachis; siphonozooids, basically polyps without tentacles, pump water into the pen.  Small stenothoid amphipods are commonly found on the pen’s surface. 

Sea pens are like the late comic, Rodney Dangerfield, in that they “don’t get no respect.”  They are often largely ignored in invertebrate zoology classes, and hardly discussed at all in many marine biology classes.  Nonetheless, they are surprisingly abundant and, in fact, may be the dominant cnidarians over large regions of the earth’s surface; areas where stony corals, other octocorals, and most sea anemones are essentially absent, the deep sea soft-sediment bottom.  The largest of Earth’s ecosystems, much of this area is characterized by the presence of sea pens.  I doubt anybody has made the calculations, but I suspect that it would a sure bet to say that the biomass of sea pen living tissue exceeds that of all other benthic cnidarians combined.

Figure 5.  A small sea pen that had been drifting across the bottom.

Ptilosarcus guneyi, the subject of this article is found throughout the Northeastern Pacific from Alaska to Southern California.  Fully expanded, large, adult individuals may extend for about 60 cm (2 feet) out of the sediments, with the base extending into the sediments another 15 to 30 cm (6 to 12 inches).  Fully contracted, these same large adults will be about 15 to 20 cm (6 to 8 inches) long.  The body color ranges from a pale cream to deep orange red.  The body morphology may remind one of a fat, carrot-colored quill pen; hence, “sea pens”; alternatively, when contracted, they may remind one more, simply, of carrots.  Internally, they contain a single large calcareous and proteinaceous style.  The size of the style is related to the age of the sea pens, and measurements of it may be used to obtain ages of individuals in a population.  Ptilosarcus gurneyi are found in shallow waters, ranging from the lowest intertidal zone to depths of about 500 feet, but are most abundant in shallow waters.  And, the animals in this species may be amazingly abundant.  In the Puget Sound areas studied by Birkland, the number of sea pens averaged about 23 pens per square meter, with about 8 of these being three or more years in age.  Sea pen beds typically reach depths in excess of 50 m, and extend laterally for dozens of kilometers, interrupted only physical features such as scouring by river currents, dredged harbors and the like.  Although these beds are discontinuous, because of the currents in the area, they are not isolated from adjacent beds.  Larvae are dispersed throughout the region, and even adult pens may move laterally great distances.  The adults can crawl up out of the sediment, inflate with water, and drift along in the currents, much like an underwater balloon.

Figure 6.  A sea pen photographed in the field, shortly after the spring equinox, a day or two prior to spawning, showing the eggs in the gastrozooids.  The extended nature of the gastrozooids is visible in the image.  Their guts extend through the leaves into the rachis where they meet and fuse with a large internal canal system that extends throughout the animal.  The eggs are about 0.6 mm in diameter.

The sea pens have a cyclic behavior pattern of inflation, feeding, and then deflation.  They may do this several times a day, and the rhythm appears more-or-less unrelated to feeding or available foods.  At any one time, Birkeland found that only about a fourth of the pens were exposed, with the rest being completely buried in the sediments, often to a depth of 30 cm (1 foot) or more.  The sea pens totally dominate and structure these communities.  Very few other macroscopic animals live in the sediments of sea pen beds, possibly because the continuous bioturbation resulting from the movement of the sea pens.

As one might expect, the shear mass of sea pen flesh in these areas is a resource that has not “gone unnoticed” by predators.  In fact, there is an amazing variety of predators that have become adapted and, in some cases, totally dependent upon the sea pen populations.  In many respects, Ptilosarcus gurneyi in sea pen beds fills an ecological position similar to the huge herds of bison that used to occupy the American Great Plains or the grazing animals of the Serengeti.  In each of these cases, whole food webs were built upon the basic primary resource species.  Sea pens are suspension-feeders eating small organic particulate material, larvae, and other small zooplankton.  In turn, they are the food of a wide variety of benthic predators.  When small, they are eaten by several, mostly small, nudibranch species.  As they grow they become too large for some of the nudibranchs, although others may still eat them.  However, as the pens grow to maturity, they become the prey of several sea star species.  At the apex of this food web is yet another sea star, which preys on those stars.

In The Water

Ptilosarcus gurneyi generally spawns in the first week following the spring equinox.  In the laboratory during that time, sunlight hitting a tank of gravid sea pens that has been shaded will induce spawning.  The eggs are large, about 600 μm across, and a mature female colony will produce upwards of 200,000 of them.  Fertilization occurs in water column.  Embryonic development occurs over about 3 days at 12º C, and results in a foot-ball shaped, mobile, non-feeding, planula larva about 1 mm long.  After about five days, planulae raised in the laboratory begin to swim to the bottom of their containers.  By inference, the same behavior in nature would move them toward the ocean bottom.  In laboratory containers, they repeatedly swim vertically downward and touch their anterior end to the sediments.  If the sediments are coarse sand, with particle diameters in the 0.250 to 0.500 μm range, they will stick to, and “settle” into that sediment and begin to metamorphose into a small sea pen.  If appropriate sediments are not available, settlement and metamorphosis may be delayed for as much as a month.  Without appropriate sediment, the animal will die.  These pens are found in an areas dominated by vigorous tidal flows and offshore currents.  In a month, the larvae could disperse over great distances.

  

Figure 7.  Drawings done from life of developing Ptilosarcus  gurneyi embryos.  Top.  The newly released ovum.  Center.  Embryo at about the beginning of the 4-cell stage; about 4 hours old.  Cleavage is incomplete and doesn’t extend through the embryo.  Bottom:  Embryo between the 4 and 8 cell stages, about 6 hours after fertilization.

 

 Figure 8.  Drawings done from life of developing Ptilosarcus  gurneyi.  Top.  The 8-celled stage is about the same diameter as a newly spawned egg; about 7 hours after fertilization.  Center.  The embryo is at the 16-celled stage; about 8 hours old.  Bottom:  This embryo is at the blastula stage, about 12 hours old.

   

Figure 9.  Drawings done from life of developing Ptilosarcus  gurneyi.  Gastrula stages; individual cells no longer visible.  Left.  Early gastrula, irregularly shaped, about 24 hours old.  Center.  Gastrula, about 36 hours old.  Right:  Late Gastrula, the embryo has become ciliated and is swimming; 2 days old.

Figure 10.  Drawings done from life of developing Ptilosarcus  gurneyi.  Top.  Early planula, about 3 days old.  Bottom:  Planula larva at 4 days old.

 

Figure 11.  Drawings, done from life, of developing Ptilosarcus  gurneyi.  Top.  Planula at 5 days.  Center.  Planula, settling, about 6 days.  Bottom:  Settled larva undergoing metamorphosis into a juvenile sea pen; about 8 days of age.  The animal is capable of contraction and elongation.

Once metamorphosis begins development to a feeding individual is rapid, with the first polyp having functional tentacles within 2 weeks of spawning.  Active feeding begins soon thereafter and given sufficient food, growth is relatively rapid.  Once the sea pens have settled, they become potential prey for many predators.  Birkeland found that small sea pens are eaten at the rate of about 200 per year per square meter by small nudibranchs.  If they can survive this period, they get large enough to avoid becoming prey for the smallest of the nudibranchs, but they graduate into become food for sea stars.  Sea pens grow at a relatively constant rate, reaching sexual maturity when they are about 24 cm (9. 4 inches) tall and five years old.

Both growth and predation rates are continuous; there is no cessation of growth upon reaching an “adult size.”  As with many cnidarians, no old age or senescence is demonstrable in these animals.  Nonetheless, they don’t live forever.  In essence, Ptilosarcus life is an exercise in “beating the odds,” and as in all such cases, the “odds,” – in this case, the odds of being eaten by a predator – are too great for indefinite success.  The life expectancy of an individual sea pen in the Puget Sound areas appears to be about 14 to 15 years.  Older animals may be occasionally found but, if so, they are very rare. Predators aren’t the only source of mortality in sea pens, nor are sea pens immune from parasites which may influence their growth and survival; however, these factors remain unstudied.

 

Figure 12.  Drawings, done from life, of developing Ptilosarcus  gurneyi.  Larva undergoing metamorphosis.  Top.  11 days.  Center.  13 days old; tentacles clearly evident; bumps on body surface are of unknown function, spicules were not present; mouth is open and a gullet or gut is evident.  Botom:  15 days old; note the development of the first pinnae on the tentacles.

 

 

 Figure 13.  Drawings, done from life, of developing Ptilosarcus  gurneyi.  Two individuals about 3 weeks old; spicules are visible in the body wall.  They have one complete feeding polyp, the primary polyp, and siphonozooids on the stalk.  The animals were actively feeding at this time and were about 3.5 mm long.  The extent of the visible gut is shown in the right individual.  The individuals were settled and growing in coarse sand.  At this point, I terminated this growth series and transplanted the juveniles to a sea pen bed in one of my benthic research study sites.  

 

Figure 14.  A juvenile sea pen, photographed in nature; depth about 15 m.  The animal is an estimated one year old.  It was between one and two centimeters (about 0.4 to 0.8 inches) high.  Note gastrozooids, and the internal calcareous style (visible as a white band).

Figure 15.  Juvenile sea pen, photographed in nature; depth about 15 m.  This animal is about two years old.  It was about 5 centimeters (about 2 inches) high.  Note: the gastrozooids, the siphonozooids (visible as bumps on the stalk), and the developing leaves.

 

 Figure 16.  Older juvenile sea pen, probably about 4 years old, about 15 cm (6 inches) high.  The internal style that can be used to age the animals is clearly visible as a white internal stripe.

 

Figure 17.  Evidence of incomplete, or attempted, predation; in both cases these partially eaten sea pens probably were attacked by nudibranchs.

   

 Figure 18.  The Predators.  These nudibranchs primarily eat the smallest pens and become common in sea pen beds shortly after the juveniles settle and metamorphose out of the plankton.  Top. Hermissenda crassicornis.  Bottom.  Flabellina trophina.  Both nudibranchs are small, reaching lengths that do not exceed about 4 cm (1.6 inches).  These species are responsible for the deaths, on the average, of upwards of 200 sea pens per square meter, per year.

Figure 19.  The Predators.  This nudibranch, Tritonia festiva, reaches lengths of about 10 cm (4 inches) and primarily eats small to medium-sized sea pens, but will not hesitate to take a chunk out of a larger one, as the above individual is about to do. 

  

Figure 20.  The Predators.  These two large nudibranchs, Tritonia diomedia (top) reaching lengths of 15 cm (6 inches) and Tokuina tetraquetra (bottom) reaching lengths in excess of 30 cm (12 inches) also eat sea pens.  Tritonia is common in sea pen beds, Tokuina are uncommon in those areas, and tends to eat isolated sea pens growing in sediment pockets in rocks.  Individuals of these two species can eat the largest of sea pens without any difficulty whatsoever.

 

 Figure 21.  The Predators.  These images show Armina californica, (top) probably the most abundant nudibranch predator that eats Ptilosarcus in the Puget Sound region.  Although solitary individuals are capable of eating a pen, these animals are gregarious and are often seen clustered over the remains of their prey (bottom).  Armina californica are reach lengths of about 10 cm (4 inches) long, and will eat all size categories of pens.

Figure 22.  The Predators.  In the areas of the sea pen beds, about 50% of the food items eaten by the rosy sunstar, Crossaster papposus, are sea pens.

 Figure 23.  The predators.  In the areas of the sea pen beds, about 98% of the food items eaten by leather star, Dermasterias imbricata are sea pens.

Figure 24.  The Predators.  The vermillion seastar, Mediaster aequalis,  preys on sea pens, among many other things.  Here a sea star is hanging on to a previously buried sea pen that is expanding and trying to dislodge it.  Pens bury into the sediments and, if stimulated, the pen will sometimes inflate, and expand in an apparent attempt dislodge the predator.  Note that the pen has lifted the sea star totally off the substrate.

 

 Figure 25.  The Predators.  The spiny sea star,  Hippasteria spinosa, eats only sea pens.  It takes a full grown star about 4 to 5 days eaten a fully grown sea pen.

 Figure 26.  The end result of the effects of all of the predators is the style.

 Figure 27.  The Green Disease.  As if predation wasn’t enough, the sea pens are subject to other maladies.  The green coloration in the pens above is caused by an endoparasitic green alga, which appears to kill the pens, albeit it takes several years to do so.

Figure 28.  Not all Ptilsosarcus gurneyi in the Northeastern Pacific are found in dense beds.  They may be found in many other habitats where sand pockets of the appropriate type occur.  The anemones to the left are Urticina piscivora, and are about 30 cm (12 inches) across the oral disk. 

During their lifetime, these pens probably reproduce about ten times.  If the average number of eggs produced by one pen is 200,000, then each female will produce about 2,000,000 eggs over her life span.  If the populations are assumed to be constant, neither shrinking nor growing, then over the life span of the female she must spawn the eggs to replace herself and her mate, indicating the odds of survival to successful reproduction by any given Ptilosarcus gurneyi individual in the Puget Sound region is about 1,000,000 to 1.  Although those odds seem pretty slim, they are significantly greater than many other marine animals such as pelagic fishes.

  Figure 29.  Juvenile Ptilosarcus settle in dense assemblages; they have to, to be able to withstand the predation pressure of the array of predators that feed upon them.

 Finishing Thoughts…

There are some things that may be taken to heart from my tale of sea pen life and, mostly, death.  First, despite their apparent simplicity, these are hardy animals capable of surviving much environmental perturbation and unless they are eaten, they have the potential of living a long time.  Second, they are mobile and capable of movement, and will leave areas that are not to their liking.   Third, although P. gurneyi  lack zooxanthellae, they have a rapid growth rate.  The Puget Sound region, the so-called “Emerald Sea,” is exceedingly rich in plankton.  One reason sea pens are so abundant in the region is all of the potential food.  They eat small zooplankton.  They probably will not eat much phytoplankton unless it is a suspension of clumped cells.  Finally, these are very neat and strikingly beautiful animals, I haven’t even touched on their bioluminescence, but suffice it to say, in a dense sea pen bed at night the blue green glow from the pens is bright enough to take notes by.   This species is as typical of the Pacific Northwest as apples and sasquatch, and yet it is almost as unknown as the giant Palouse earthworm.   And that is a pity!

References:

Birkeland, C. 1974.  Interactions between a sea pen and seven of its predators.  Ecological Monographs. 44: 211-232.

Chia, F. S. and B. J. Crawford. 1973.  Some observations on gametogenesis, larval development and substratum selection of the sea pen Ptilosarcus gurneyi. Marine Biology. 23: 73-82.

Kozloff, E. N.  1990.  Invertebrates. SaundersCollege Publishing. Philadelphia. 866 pp.

Ruppert, E. E, R. S. Fox, and R. D. Barnes. 2003. Invertebrate Zoology, A Functional Evolutionary Approach. 7th Ed.   Brooks/Cole-Thomson Learning. Belmont, CA. xvii +963 pp.+ I1-I 26pp.

Shimek, R. L. Unpublished Observations.

Predators In The Sand, Or…

Monday, September 5th, 2011

Thoughts On The Evolution And Natural History Of Scaphopods.

Why Here And Why Now?

This post is, obvously, the continuation of a series dealing with scaphopods and some  of the data I will be posting subsequently are also to be found on one or another of my website’s scaphopod pages.   However, these blog entries are not strictly duplicative; I have added a number of new data and I have  altered some of  the information to reflect my present thoughts.   Some of the ideas and data to be  presented here are somewhat iconoclastic, and contrary to what some authorities have proposed.  It is unlikely I will get the opportunity to publish these ideas in more formal, peer-reviewed, jounals, and as a result I thought this is an appropriate place to let the ideas see some glimmer of the light of day, albeit dimly and through some wet mud.  To the questions of “Why Here and Why Now?”  I think the reasonable answers are, “Because I think  this is an appropriate place and it is time.”  Or phrased another way, “Why Not?”

 One of Three Groups…

The scaphopods are the last of the classical molluscan classes to show up in the fossil record, with arguably the first unequivocal scaphopod being Rhytiodentalium kentuckyesnis Pojeta & Runnegar, 1979.  However, this unequivocality is not likely the case; the specimens of Rhytiodentalium are all significantly altered fossils, and from personal examination, it is impossible to tell exactly what they are.  Although some of them match the general shape of modern – and presumably – highly derived scaphopod shells, these “shells” appear to be comprised of small pelletized material.  It is unclear if these pellets are the result of significant or minor diagenesis.  In the first case, the shells could considered as scaphopods.  In the second, they would have to be something else, perhaps, some sort of worm tube.  I think the latter is much more likely than the former.

The term “armchair quarterback” has been coined to describe those individuals who after watching a football game at home on the “aptly-named” boob tube, dissect a quarterback’s performance and describe, a posteriori, what he should have done.   Of course, such a critique, if that’s what it may be called, is done without the experience of being under the tremendous pressure of the momnet on the field of play, without the sport’s equivalent of the “fog of war” clouding information input and, most importantly, it is done with the precision vision of hindsight.  Of course, in the armchair experience, errors made on the field become glaringly obvious.   One of the prime theories of scaphopod evolution is that scaphopods arose from an ancestor that either was in the extinct class, Rostrochonchia, or pehaps in its ancestral group, is the malacological equivalent of such airchair quarterbacking, however, with one glaring exception.  It is undoubtedly wrong, most likely as a result of being proposed by individuals who have had no experience examining or studying live scaphopods or, indeed, live animals of any sort..

There are a number of very serious problems with the Scaphopods from Rostroconchs derivation, not the least of which is that the scaphopod shell is univalved and tubular, while the rostroconch shell is bivalved of various non-cylindrical shapes.   Additioanally, the scaphopods are all predators or scavenger/predators; as a result, they must move; no predator on infauna waits for the prey to come to it.  Then, the scaphopod radula, the structure used to macerate, break, crush  or smash prey is the largest radula relative to the adult body size in all the mollusca.  On the scale of the organisms, it is a truly massive structure.   This massive radula is presumed to have been derived from an ancestor in the same group that is supposed to have given rise to the bivalves.  However, not only do the bivalves  lack the radua, but also any remnant of the head it is found in.  While the scaphopod head is reduced and kept within the shell, it is present, and has a relatively large brain, also a structure missing in the bivalves – and presumably their rostroconch ancestor.  The rostroconch shapes vary quite a bit, but one thing that is evident in all of them is that they are not streamlined and capable of easy movement through sediments.   Indeed, with the shapes typically found  in rostroconchs, it is quite likely, that like some oddly shaped infaunal bivalves today, they did not move at all as adults.  Scaphopods, on the other hand, are all mobile and many of them, given the appropriate stimulus, are capable of bursts of relatively rapid motion, after which they often stop, construct a feeding cavity and feed.  Given the sizes of the adult scaphopods, the  number of body lengths that they are able to move in any given amount of time, and the media that they move through, it is quite reasonable to consider many of them to be “high speed” predators.  Finally, recent molecular genetic work shows them to be grouped with the cephalopods, not the bivalves.

I think it is likely that one of the first branchings of the ancestral molluscan stock gave rise to a predatory organism that had a tendency to develop or elongate in a dorso-ventral direction.   In turn, this ancestor, over time, gave rise to three successful clades, eventually leading to the crown groups of the cephalopods, gastropods, and scaphopods.  All of these groups are all characterized by dorso-vental flexing in the visceral region, a well-developed radula, and elaborations of the cephalic tentacles.

Each of the three dorso-ventrally flexed groups shows particular adaptations and modifications for its primary habitat.  The cephalopods are highly successful predators in the pelagic enviroment.  Gastropods have radiated into virtually every possible niche except aerial flight, and are found in all terrestrial, fresh-water, and marine environments, although their ancestral habitat was the marine benthic epifaunal environment.  Scaphopods have become highly adapted for predation on organisms living in unconsolidated marine benthic sediments.

Cadulus tolmiei in situ, modified from Poon, 1987.

The above image shows Cadulus tolmiei feeding in sediment, cb= captacular bulb, dd= digestive diverticula, fc = foot cavity, g = gonad,  m= mantle,  pa = posterior aperture,  s = shell,

References:

Pojeta Jr., J. et. al. 1972. Rostroconchia:  A New Class of Bivalved Mollusks. Science. 177: 264-267.

Poon, Perry A. 1987. The diet and feeding behavior of Cadulus tolmiei Dall, 1897 (Scaphopoda: Siphonodentalioida). The Nautilus: 101: 88-92.

Steiner, G. and H. Dreyer.  2003.  Molecular phylogeny of Scaphopoda (Mollusca) inferred from 18S rDNA sequences: support for a Scaphopoda–Cephalopoda clade.  Zoologica Scripta. 32:343-356.

More to come…

Until then,

Cheers!!!

More Scaphopod Information – Including Some Ancient Scaphopod Jewelry

Friday, August 26th, 2011

 Scaphopod Connections

Over the past few days, I have finished scanning my images of Native American scaphopod jewelry and decorated clothing, all of which were photographed in 1987 in the Burke Museum on the University of Washington campus in Seattle.  Some of the Native American dentalium jewelry/clothing images that I have are REALLY impressive, not only for the wealth they contained, but also for the tremendous skill of the remarkable women who made them.  Somehow, I wish I could find something like the shawl in the image below in an old trunk in my garage, and take it to the appraisers on The Antiques Roadshow.  It would get the attention it really deserved.  Ah… well.  All I am likely to find in old trunks in my garage is old trash covered in old dust.

 A shawl, made by a seamstress and master craftswomen from one of the Plains Tribes, in the mid-to-late 19th century.

This is a shoulder wrap or some sort of vestment, I neglected to photograph both sides in 1987, when I took the image.  I would estimate that there may be close to a 1000 Antalis pretiosum shells in this item.

Not surprisingly considering their shapes and durability,  scaphopod shells were widely used in ornamentation elsewhere and elsewhen throughout history.   The following image was taken by Don Hitchcock in from the Dolní Věstonice Museum in the Czech Republic, which has some wonderful artifacts recoverd from an ice age mammoth hunter’s site.  

dolniimg_2014b

A reconstructed necklace made from fossilized Dentalium badense shell fragment artifacts recovered at the Dolní Věstonice site in the Czech Republic.  The artifacts at this site have been dated with Carbon-14 to about 29,000 years ago.  Photo: Don Hitchcock donsmaps.com

In one of the more bizarre coincidences I have had recently, I found the above image and information with the assistance of Mr. Google and associates.  I hadn’t seen it prior to findinig on the web, but I knew that there should be ancient European, Asian or African dentalium work illustrated somewhere on the web, and charged ahead to find something I might use.  I found this image, and it fit the bill of what I wanted, and I went to track down some information about it, including where the Dolní Věstonice site (which, from reading the information at the site, I realized I must have read about it sometime ago, I recollected nothing at all about it ) is located. 

This Google Earth image shows where the Dolní Věstonice site is located.  The other site indicated, the Frydek-Mistek region, is  where my ancestors, at least back to before the mid-1700’s, lived. !!!  My great-great-grandfather was one of four brothers that migrated together from this area to the US (Texas) just after the Civil War.

Nobody knows, of course, what happened to the descendents of the people who made and used the scaphopod shell necklace, or even if they left descendents at all.   But I think it could be possible -stretching possibilities very thinly- if those descendents remained in that area, that maybe some of the genes of the person who made the scaphopod necklace may have decended to be in the genome – some 28,000 years later – that directed the growth of my scaphopod-studying body.

In closing this entry, I must thank Don Hitchcock for his gracious permission to use his fine image of the scaphopod necklace.  Don has an immense array of web information about the paleolithic period throughout the world, and I have linked to his site in my blogroll.  It is well worth a visit.

Until later,

Cheers,

Starting Something New

Tuesday, July 19th, 2011

Nudibranchs

For quite a while I have wanted to post a number of my underwater images which were taken from 1975 through 1994, mostly in a few of the shallow water environs of the Pacific Northwest, a.k.a. the Northeastern Pacific.  Most of these were taken to be illustrative, that is to show the animal or organism, primarily for lectures or in presentations, they were not meant to “artsy” images, although some certainly turned out that way.  I finally have bitten the bullet, and am scanning a lot of these images into high-definition digital form, this being largely facilitated by the purchase of an external hard disk drive (HDD) of terabyte capacity, so that I actually have a convenient place to store the images.  Judging from the size of the scanned images, I may well fill that HDD.  However, I obviously can’t post such high definition images here, nor can I post them all, as I estimate I have well over 5,000 images.  Consequently, I have decided to post a few every few days for the foreseeable future. 

Unfortunately, the posted images are really not the best quality; the images scanned from my slides average about 80 Mbytes each, so, the images posted here are really quite low in resolution.  Sorry about that, but it can’t be helped.  In my scanning, the order is not random, but it is also not taxonomic.  It is “slide holder order.”  I had/have arranged my opisthobranch slides in slide holders in a loose leaf notebook with the nudibranchs first, but within that group they are in more-or-less haphazard order.  If that bothers you, exit now and save yourself the heartburn.  Once I get them all scanned, I will arrange them in some sort of logical order, but that is in the future.  

The very diverse and species-rich array of animals grouped under the name “Opisthobranchia” were, until recently, thought to be related.  That is no longer the case, and while some subgroupings within the old group, such as the nudibranchs, are good taxonomic groups, the term “opisthobranchia” is now obsolete and used only as an informal term, and one I suspect will die out over the next few decades.  I hope you enjoy the images and the commentary that goes with some of them.  The taxonomic nomenclature (i. e. the names) used in the opisthobranch image postings follows that given in the fine photo reference book:  Beherens, D. W. and A. Hermosillo. 2005. Eastern Pacific Nudibranchs. A Guide to the Opisthobranchs from Alaska to Central America. Sea Challengers Publications. Monterey, California. vi + 137 pp.  If I have made any mistakes in the listing or image names, those are mine and mine alone.

Hermissenda

Hermissenda crassicornis, the opalescent nudibranch.  Photographed at a depth of about 10 m on the 4th of July, 1992 in Barkley Sound, Vancouver Island, British Columbia, Canada.

A pair of Hermissenda crassicornis, the opalescent nudibranchs.  These were photographed at about 10 m on the 14th of October, 1983 near Ohiat Isand in Barkley Sound, Vancouver Island, British Columbia, Canada.

These nudibranchs are not social animals and their appearance together is probably happenstance.  However, they may be getting together to mate.  Unlike many other nudibranchs, particularly the dorid nudibranchs in which copulation may take many hours, mating in Hermissenda is anything but sluggish.  As with all nudibranchs, they are hermaphroditic and mating is reciprocal.  From start to completion, copulation takes but a small fraction of a second.  

Hermissenda crassicornis, the opalescent nudibranch.  Photographed at about 12m depth, on the 2nd of June, 1982 in Barkley Sound, Vancouver Island, British Columbia, Canada.

The above opalescent nudibranch appears to be on a rock with brown algal filaments on its surface, but that is misleading.  The scene is one of a small patch reef created by the annelid worm, Dodecacaeria fewkesi.  What appears to be brown algal filaments on the substrate are actually masses of tentacles arising from the worms whose calcareous tubes are cemented together forming the reef. 

And there is more going on!!!

The tall structures in the background are hydroid colonies; probably the nudibranch would be eating the hydroids if it were on them.  The small white blobs on the hydroids are either individuals of another nudibranch, from the genus Doto, or that species’ eggs.  During the spring, everything in this region grows like crazy, particularly those animals, such as the hydroids, that feed on plankton, which is very abundant.  In this case, the hydroids, of course, feed on small zooplankton. Individuals of Doto species feed on the hydroid polyps and their populations bloom right after they hydroids have their growth spurt.  These small nudibranchs, about 3 or 4 mm long, can have population densities exceeding 5,000 per square meter, and will be featured in an upcoming post.

Dodecaceria fewkesi, the “reef building” cirratulid worms.  Photographed on the 28th of April, 1984 inDodger Channel, Barkley Sound, Vancouver Island, British Columbia, Canada.

These worms secrete the calcareous tubes that they live in.  Dodecaceria individuals aggregate together, probably due to asexual reproduction as well as larval recruitment.  In doing so, their calcaeous tubes fuse forming, first, what appear to be small rocks with worm holes in them.  Later, as time goes on, these rocks grow by the addition of more worms.  In doing so, they create one of the few types of reefs, other than those made by corals, that are biogenic, or made by living organisms.  These worm reefs are never very large, but they can be as much at 20 to 30 (6 to 9 m) feet long and 6 to 10 feet (2 to 3m) high, or as big as some coral patch reefs.

A portion of a small reef built byDodecaceria fewkesi, the calcareous-tubed hair worm.  Photographed on the 29th of April, 1983 in Pole Pass, between Crane Island and Orcas Island, in northern Puget Sound, Washington, USA.  The slightly “foggy” appearance to this image is due to small plankton in the water reflecting my strobes’ light. 

This image shows the small “rocky reef” made by the hair worms.  This area in the San Juan Islands of Washington, was one of my primary research study sites in the early 1980s.  In addition to the small patch reefs made by this worm species, there are other, much larger, reefs at this site that are made by a different type of worm, the sabellariids, and I will probably post images of them in the future.  Most biologists don’t realize that corals are not the only reef forming animals, and when told of these worm-built reefs, often respond with disbelief and incredulity.  Nonetheless, such structures are reasonably well-known and described in the scientific literature. 

As with coral reefs, these worm reefs are “hot spots” of local species diversity.  However, there small size and lack of much 3-D heterogeneity, limits the number of other animals that live with them.  Nonetheless, opalescent nudibranchs, and the hydroids they feed on are often common on these reefs.   Due to the distance from the reef, not much other life is recognizable in this image, though.  The large white blob is probably a contracted plumose sea anemone (Metridium sp.), which when inflated fully would be a couple of feet high.  The golden crescent near the bottom, is the aperture of a large scallop (Hinnites sp.) that is found in the area.  These animals cement their shells to rocks, and unlike most scallops are immobile when they are adult.  That individual is probably about four inches (10 cm) across.  

Flabellina

 There are lot of small aeolid nudibranchs found on, and eating, hydroid colonies or other cnidarians in the spring in this region.  Here are a couple of shots relating to, and of, Flabellina trilineata.

The orange structure is a colonial hydroid, Garveia annulata, that was occasionally common in some areas that I dove in.  The hydroid colony in this image is a couple of centimeters long. Notice the large orange “balls”  (reproductive polyps), they are about 1/4 mm in diameter.

The three-lined nudibranch, Fabellina trilineata.  This little nudi reaches lengths of about 1.5 inches (36 mm) or so, and is commonly found in the spring in rocky areas in the Pacific NW subtidal regions.  It,  like many aeolid nudibranchs eats hydroids, including Garveia.

This image shows a baby F. trilineata (notice the rows of tiny cerata growing on its back) eating Garveia.  The nudi is about 2 to 3 mm (about 1/8th inch) long.  You can get an idea of size by noting the reproductive polyps and comparing this image with the images of Garveia, above.

One of the activities I tried to do at times during my diving career was to take “extreme” macro shots of various invertebrates in the field.  I had an apparatus that allowed me to get an image magnified up to about 12x on the slide; so, if the animal was 2 mm long, the image would be about an inch long on a 35 mm slide.  In this case, the nudibranch in the last image above was magnified about 8 times.  There were a lot of technical problems with taking these images, not the least of which was that the object to lens distance was very small, and that it had to be accommodated within my camera’s underwater housing.  Given the water currents in the areas where these images were taken, even holding one’s position during the water flow, euphemistically referred to as slack water, could be difficult.  The large camera and strobe housing caused an immense amount of drag, and severely limited my mobility.  Other problems included looking through the viewfinder of the camera with a scuba mask on, and so on…  Suffice it to say getting any sort of image was a problem.

The major difficulty, however, was getting enough light hitting the very small object to reflect back, passing through the underwater housing plastic, then the lens, and then the bellows that was on the front of the camera, and into the camera to properly expose the film.  I began to feel like I needed a tactical nuke to take the picture.  If I was able to successfully expose the object so that the slide was properly exposed, it sometimes felt like I need to produce so much light that it would vaporize the object I was taking photographing.

In the above image of the baby Flabellina on Garveia, the digital software “pushed” the exposure quite a lot, but doing so increased noise, and that noise is particularly apparent at the low resolution I must use here.  That is why the image is a bit blurred.  It can’t be helpped, sorry.

The next species of choice is Flabellina trophina, one of the more blah of the these normally spectacular wee beasties.  Nonetheless, I have a fair number of images of it, as the species was common in some habitats I was investigating, and there were often not a lot of other animals visible there, so rather than return to shore with only half a roll of film shot off, I would take images of individuals of this species of nudi, and sometimes a few other critters.

Flabellina trophina.  Photographed near Seattle in central Puget Sound, WA. in 10 m of water in 1982.

A head-on view, this image shows to advantage the extensions of the brown or tan digestive gland up into the cerata on the animal’s dorsum.  “Cnidosacs,” specialized structures containing undischarged nematocysts from the animal’s previous dinners are located at the tips of each ceras and their presence is emphasized by the bright white coloration.  This is probably aposematic or “warning” coloration for any visual predator, in these cases either a fish or crab that might consider this nudi a tasty snack.

Flabellina trophina.  Photographed near Seward, AK in 10 m of water, in 1982.

This shows the animal in a side or lateral view; F. trophina can reach lengths of about 50 mm, or 2 inches.  The structure visible on the animal’s right shoulder is the combined anal and genital apertures.  All nudibranchs have their genital openings in this region, but the anus may vary in position, and that is – as one might guess – one of the characteristics defining each different subgrouping within the nudibranchs.  The aeolidacea all have these apertures in position as shown in this individual. 

Flabellina trophina.  Photographed south of Seattle in central Puget Sound, WA. in 12 m of water in 1988.

I have no quantitative data, but my notes list several observations of this species feeding on sea pens (Ptilosarcus gurneyi).  I was working on photodocumenting the events occurring in sea pen aggregations (called sea pen “beds,” for no logical reason known to human cogitation).  Over some 20 plus years, I made, maybe, 150 dives in this habitat and took several hundred images. There will be slides of many other different animals posted during these excursions through my slides that were taken in the sea pen aggregations.  Starting with some nice research by Chuck Birkeland the natural history and “ecology” of the sea pens in the Puget Sound region are probably the most well known of all pennatulaceans.  In any case, I was photographing F. trophina in the beds not because it was documented to feed on the sea pens (it was not, even though I found that it is a common predator on them – or at least it was when I was actively diving in those areas), but rather because it was common and somewhat attractive, and sometimes, I just wanted to take its picture. :-) .  I took the above image because it shows a lateral view of the animal with its snout elevated which is a common posture.

Flabellina trophina.  Same images as above. 

While I was preparing the scanned image for this post to the forum, which involved making lower (much lower) resolution images, I noticed what I thought might be artifacts due to fine hairs that got on the slide prior to it being scanned.  And, gee, living in a house with a large hair factory, one that specializes in producing very thin, fine hairs (a.k.a. – my true buddy, Casper = “A Maine Coon Cat” = giant fur ball).  I figured that if these were, indeed, fine Casper hairs, I would have to reclean the slides and try scanning them again.   The “hair” images/artifacts are circled, and if one examines the image above this one, it is quite possible to see them without the circles.  There are a lot more faint “hair-artifacts” visible than are circled.  

My buddy, Casper, a generator of loose, fine hair, but not guilty of being the source of “hair-like” images on my nudibranch slides. 

Flabellina trophina.  Same images as above. 

When I examined the fine “hairs,” I found that Casper was off the hook, they were not artifacts at all, but were actually part of the original image.  They were microscopic phytoplankton floating by in the water as I took the images.  As I described above, I could photograph microscopic subjects.  Well, here is the inadvertent proof of that statement!  And, it is something that I had never seen on the image before this scan! 

I further enlarged the portions of the images in the red circles and included them in the original image.  They are shown outlined in red and are indicated by the arrows.  Note the “zig-zag” structures.  Well, those structures are not 2-D zig-zags, but rather 3-D helices of chained diatoms.  Here is a link to a photomicrograph showing similar diatoms in a better view.  

WOW!!!  I think this is REALLY neat, because it shows how what appears to be the relatively clear water in a photograph of an underwater scene may, in fact, be filled with plankton that are just below the resolution capabilities of either the camera or the printer or scanner to show.  I have often heard a comment to the effect that a given tropical coral reef image shows water so clear that it is “obvious” that there is no plankton in it.  I wonder how many of those images would show microscopic plankton of one sort or another if they had been taken with a better camera or printed in better manner.  

No plankton present…  LOL!!!  Obvious, INDEED!!!

More images soon.

Until then,

Cheers, Ron