AHABS... Issue Two

How To Get There From Here; Some Techniques For The Rearing Of Larval Invertebrates

By

Ronald L. Shimek, Ph. D.

What do I know about raising larvae?

One of the many problems confounding the reef aquarium hobby is that of “instant experts.” All it takes to become an “expert” is a computer, a word-processing program, and chutzpah. Chutzpah – What a great word! It certainly is an appropriate descriptive term for many of the reef aquarium “authorities” that seem to appear as if by magic. I suspect all of the people reading this article know of my love for “ THE ” language. English or, I suppose, in my case, “Americanish,” is a glorious instrument. Wielded well it can be as blunt as a bash in the butt with a bass fiddle or as surgically precise as a laser scalpel. One of the great things about this language is its ability to incorporate words from other languages. In my humble opinion, what makes the American version of the mother tongue so much more exciting than other versions is its continual modification by immigrant America . The glory of the American experience is its continual reinvention by the melding of cultures; modern Americans can trace their roots back to … everywhere. I have Swedish, Irish, French, Cree, and Czech/Ukrainian ancestry and I am by no means exceptional. To paraphrase an advertising slogan, the typical American is of “Heinz ancestry;” all 57 varieties. That melding of cultures is reflected in our language. Chutzpah, of course, is a word of Yiddish origin and, it means “unmitigated gall,” and many so-called reef aquarium experts have it, and nothing else, in excess.

What isn't apparently necessary to become a well-thought of and highly respected authority is either experience or knowledge. There has been quite an array of individuals who have appeared and almost instantaneously become experts, primarily it appears, by their ability to make their selves heard or to self publish a book or a magazine. There is a single, and real, benefit to self publishing; it is easy, virtually anybody can do it - as this article plainly attests to. On the other tentacle, there is no critical review of the published material. As few of these authors have ever submitted their materials to an unbiased or thorough editor, or have any concept of “editing” either for grammar or content, the amount of trash that gets published has increased dramatically in recent years; in direct proportion to the ease of publication. While the old way of publishing, where one submitted a manuscript to an editor who then reviewed, edited, and sent it back to the author for revision prior to publication, was time consuming and fraught with the potential for rejection, it also tended to weed the garden. Unfortunately, as a result of either direct (where the author does it all) or indirect (where the author owns or has a controlling interest in the publishing company) self-publication, I think the garden of reef aquarium references is a very weedy plot, indeed.

So, in the light of the above tirade, why do I think I am qualified to write articles about raising invertebrate larvae? And, probably more to the point, why should you listen to me? As regards the first question, it might seem that I am ill prepared to offer advice about raising larvae. After all, I have generally described myself as an ecologist who studies predator-prey interactions in...


The Animal as a Life Cycle – A Very Brief Introduction To Invertebrate Larvae As Illustrated With The Trochophore.

By

Ronald L. Shimek, Ph. D.

When most people think of animals, they think of them as the definitive adult stage, and if they think of larvae at all, those larvae are perceived of as being “incomplete” and “transitory” stages that are not quite the animal in question, that lead to the definitive adult. However convenient, and however ingrained, this is really an improper way to think of any organism. Organisms should be conceived of as life cycles, with no single stage any more important than any other, for mortality can occur at any part of the life cycle. The animal is just as dead if it dies as an embryo as if it dies as an adult. Looked at another way, a sexually-reproducing adult animal is really nothing more than a larva's way of reproducing itself.

So what is a larva?

It is difficult – and unfortunate - that to discuss larvae and larval biology one must delve into the arcane world of biological jargon. For this I apologize, but as you will see if you continue to read on, such terms save a lot of space. To help with understanding these terms, I define these terms when they are first used, and put them in bold type.

A larva is a life stage that is typically specialized for growth and often, particularly in marine animals, dispersal. In the technical world of animal development, several different – and often relatively discrete - stages between egg and adult may be recognized, with limits to each. Gametes are the only parts of the animal's life cycle that contain only half of the normal chromosome complement. In the animal kingdom, gametes always come in two discrete sizes. By definition, the organism that produces the larger gamete is the female , and that large gamete is an ovum or egg. The smaller gamete is the sperm , and the animal producing it is the male . When a sperm and egg combine, the process is referred to as fertilization, and the resulting “fertilized egg” is referred to as a zygote . Once cell division starts, the zygote is no more, and the organism is an embryo . The start of the larval period is less definite, as it varies with the animal group. Generally, when the developing animal becomes fully mobile, it is termed a larva (plural = larvae ) . When the larva grows or changes into a form similar to the adult, but lacking reproductive structures, it is called a juvenile . The only difference between a juvenile and an adult is that the latter is reproductively mature...


Reef Tank Plankton - A Partial Success For A Necessary Component

By

Ronald L. Shimek

Planktonic Definitions

In natural reef ecosystems planktonic organisms are exceptionally important and it is likely that they are no less important in our artificial reef microcosms. Plankton may be defined as those organisms living in water without the capability to move significant distances against water currents. In contrast are the nekton , those organisms that can swim against water currents. Generally plankton can be described by either their size or their taxonomic group. In discussing these organisms it is easy to get lost in a jumbled juggernaut of juxtaposed jargon, so the tendency might be to avoid the terms altogether. Unfortunately, such avoidance may reduce the discussion to one of triviality, so I do need to define and discuss some of the terms briefly.

Taxonomically, plankton can be subdivided into animal plankton (= zooplankton ), plant or algal plankton (= phytoplankton ) and bacterioplankton ( 1; 2 ) consisting of bacteria and cyanobacteria. Zooplankton and phytoplankton also include feeding and photosynthetic protozoans respectively. Generally, zooplankton are larger than are phytoplankton which in turn are larger than bacterioplankton. The largest plankton are likely siphonophores , some of which may reach 30 m or more in length, the smallest probably include viruses, if viruses are considered to be alive.

When categorizing the plankton by size, it is important to realize that the size distributions of the various plankton categories are arbitrary – and somewhat capricious. One man's femtoplankton is often one woman's picoplankton ; it is impossible to know beforehand what the terms mean, one always has to look up and determine what they mean in the context of the article . To paraphrase Ronnie “If you've seen one redwood, you have seen them all” Reagan; “Trust, but verify” the meanings. They were initially based on the sizes of the holes in the net meshes used to collect the organisms. Obviously, larger planktonic organisms may be captured by pulling a net through water and the size of the net mesh influences the size of the captured organisms. Generally standard plankton nets catch organisms greater than about 200µm (0.008 inch ) in size. Planktonic organisms less than 200 µm are often referred to as microplankton and the sizes encompassed by this term can be subdivided further based on the organisms' size into micro-, nano-, pico-, and femtoplankton . The last three groups cannot be collected using nets; instead water samples are either centrifuged to concentrate the organisms, or pumping them through very fine filters, or allowed to settle on some indicator substrate. These very small planktonic organisms, primarily bacteria, blue-green algae, and small protozoan algae ( coccolithophores ; 2 )

are exceptionally important, possibly accounting for as much as ¾ ( !!! ) of all the photosynthesis in the oceans ( Ayukai , 1991, 1992; Nybakken, 1997). Nevertheless, there are absolutely no data on their presence in our reef systems.

The array of organisms that constitutes the plankton consists of some organisms that spend their entire life in the water mass as plankton, and others that spend only a portion of their life there. Most coral reef organisms, including most corals, sea anemones, soft corals, clams and fishes, are...

 

Ron Shimek