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Natural History They sprout from beneath rocks like orange carnations, ooze along the bottom at the speed of an hour-hand, or slurp their way through rich organic mud. They are everywhere from the intertidal zone to the deepest parts of the ocean. Like a miniature herd of gnus trundling across the abyssal plains, they graze on the rich organic snow that has drifted down from above. This successful group of organisms is testament to 540 million years of evolution from the time when the ancestors of sea cucumbers and their relatives first appeared in the ocean. In contrast, it may seem petty, for some humans to spend their careers simply trying to classify and put names on these and other animals. But, to communicate the results of biological research to colleagues around the world, biologists need a well-defined set of scientific names. Revising, defining and creating new scientific names is the essence of what many museum curators do. In the vast array of marine invertebrates of British Columbia, there are still many undiscovered and unnamed. One could choose just about any invertebrate group in British Columbia waters and find new species, new geographic records, old descriptions that need updating, or misidentified species. I began studying sea cucumbers when I naively chose to prepare an identification handbook for sea cucumbers, thinking they were a well known group. Little did I know that ten years later I would still be trying to figure them out! But, I have made some progress.
My formal study of sea cucumbers (Phylum Echinodermata: Class Holothuroidea) began with the donation of a collection to the Royal BC Museum from the Pacific Biological Station, on the condition that I prepare a technical report on their identification. I soon realized that the available literature was inadequate to identify a number of species in our collection. The report was published in 1984 but it contained several question marks and tentative identifications. So began my journey into the taxonomy and systematics of sea cucumbers. Taxonomy is the study of classification and comes from the Greek word taxos meaning order. Systematics is a broader study that seeks to describe the interrelationships and evolutionary pathways of living organisms. Several years earlier, while scuba diving at Tasu on the west coast of the Queen Charlotte Islands, I spied a brightly coloured sea cucumber. It was about the size of our common California Sea Cucumber (Parastichopus californicus) but strikingly different in colour and in the size of its papillae. Was it just a colour variant or had I stumbled on something new to science? Surely something this large had not been over-looked by previous workers. Back at the lab I would surely find a reference about it. Such was not the case. I was frustrated by the lack of literature so I put the specimens on the shelf to look at later. That was the beginning of a task that would finally result in the description of the White Spined Sea Cucumber (Parastichopus leukothele) in 1986.
Figure
3: Skin ossicles from
Figure
1: Cucumaria
pallida--although quite 
As each new species evolved, the ossicles changed
with it, so each species has uniquely shaped ossicles. This is most fortunate
for a curator, who often has to identify colourless preserved specimens
in museum jars. I have discovered new species both in the field and in collections.
One that I described recently with Lisa Kirkendale escaped my notice for
many years because it resembled another common species. It was only after
learning that the eggs of the animal in question were different, that we
checked the ossicles and internal anatomy and found consistent differences
from other species. That species, called Cucumaria pallida, turns out to
be quite common in British Columbia and has been found all the way from
southeastern Alaska to Point Conception in California (Figure 1).Figure
4: Skin ossicles and segments of the 
Some similar species can easily be confused,
not only by the novice, but also by non-taxonomic researchers working on
other aspects of biology. In a study utilizing blood proteins to document
species differences, the author concluded that a small black species known
as the Tar Spot Cucumber (Cucumaria pseudocurata) was synonymous with the
Black Brooding Sea Cucumber (Cucumaria curata). However, it turned out that
the researcher never had a true specimen of C. curata so naturally all the
specimens gave similar results. That conclusion got into the biological
literature and even now, that confusion persists.
Sometimes "word of mouth" causes taxonomic problems. Another common species that attaches to rocks and shells and is armour-plated was misidentified for many years, based on a casual identification by an expert. The species identified as Psolidium bullatum by most reference books turns out to be incorrect. When I read the original description of P. bullatum it did not match the characteristics of the animal that is identified in most publications as P. bullatum. The true P. bullatum is a deep water species from the Aleutian Islands. The one we have in the shallow waters of British Columbia is now being described as a new species.
I recently identified some species from British Columbia known previously only from the North Atlantic. There are very few species known in both oceans. The question arises, did it arrive here from the Atlantic through normal dispersal mechanisms? Or, did this species originate in the Pacific and migrate to the Atlantic via the Arctic during a warm phase? Or did it arrive here via some artificial means, such as in a freighter's ballast tank or with some live commercial marine species? Or, are there some subtle differences between the two forms that I have overlooked and they are actually different species? These types of biogeographic questions are a natural outcome of taxonomy. How did these species get where they are? There are no easy answers to these questions. However, there is one method that might help. Figure
2: A calcareous ossicle from the skin of a 
New developments in the analysis of DNA
(Deoxyribonucleic acid) have made it easier to study differences among organisms
at the genetic level. Species that do not have obvious phenotypic differences
(often called sibling species) may be detectable with these methods. I am
collaborating with Dr. Michael Smith and his colleagues at Simon Fraser
University in a study of sea cucumbers. Several taxonomic problems have
been cleared up using DNA, and we have also been able to confirm some tentative
conclusions based previously on morphology. The percent change in the sequence
of bases in a segment of DNA from two species provides an estimate of how
long the populations have been separated. By analysing a group of species
we can construct a phylogenetic tree, a branching diagram that approximates
how each form might have evolved.
My goal in these studies is to publish an identification manual for sea cucumbers that is easy to use, accurate and complete. The manuscript for an identification handbook that will cover all the known shallow water species from southeastern Alaska to Puget Sound is nearing completion. The book will document the present state of our knowledge for each species and point out the areas that need work. It will contain photographs of live animals for field identifications and some details of skin ossicles to confirm the species. I hope it will stimulate much needed research on the life histories of these animals. So through curatorial research here at the Royal BC Museum, the identity of a few more species has been clarified. Biologists studying these animals will have a single reference to identify sea cucumbers, enabling them to report their findings to their international colleagues and state with confidence what species their results are based on. This article was first published in Cordillera, a magazine for British Columbia naturalists. For subscription information to Cordillera, please write to: the Editor, Cordillera, Box 625, Kamloops, BC V2C 5L6
References
Philip Lambert, Curator
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