Monday, May 19, 2008

Blog #2: Six-Foot Sea Cucumbers

I am taking a rare and short break from intensive ocean biodiversity sampling to write this entry. My base of operation is the National Oceanographic Research Center in Nosy Be, an island off the northwest coast of Madagascar. I am here with a team of marine scientists--Dutch, French, American, and Malagasy--who are engaged in an underwater assessment of coastal marine life in this part of the world. The project (BIOTAS) has the goal of characterizing the region's biodiversity (land and sea), and examining the natural processes that have led to the geographic distribution patterns among multiple groups of organisms in
the southwest Indian Ocean.

The above photo shows the center's lab space as you approach from the water. Inside this building is where our group works well into the night processing all the material collected during dives.

Among the researchers here are experts in fishes and invertebrates. I am part of the invertebrate team, and am studying the sea cucumber fauna together with Dr. Gustav Paulay and Francois Michonneau of the Florida Museum of Natural History. Sea cucumbers are echinoderms, a group of animals that includes starfish, sea urchins, brittle stars, and feather stars. There are "sea cukes" that indeed have the dimensions of a cucumber you might slice into a salad, though body length among this group of animals ranges from a few millimeters to over 9 feet, and some can weigh over 10 pounds. They are found from shallow shores to abyssal seas, and are probably the least well studied of all large and conspicuous marine animals. Roughly 1600 species are described, though many more remain to be discovered.

One fascinating characteristic of sea cucumbers is best seen under a microscope. Unlike starfish and sea urchins that construct large continuous skeletons observable on many a beach walk, sea cucumbers instead have thousands of tiny skeletal pieces or "ossicles" embedded mainly in their body wall. These ossicles take on ornate shapes as indicated by the descriptive names used for the various types: buttons, tables, rosettes, rods, etc.

During the first few days of our expedition, we have seen many synaptid sea cucumbers, such as the one photographed above (Synapta maculata). These long and slender cucumbers have a body wall about as thin as tissue paper, and a diameter about equal to that of a stick of pepperoni. Colors can vary from bright pinkish-orange to greenish brown with dark bands. We saw animals on this trip that were up to six feet long!

If you touch one, the point of contact adheres to your body like glue. This is not caused by any chemical adhesive, but the mechanical action of the animal's ossicles which are shaped like boat anchors. It is these anchors, occurring in the thousands along the surface of the body wall, that cause your hand or wetsuit to become stuck to the animal. (A quick flick of the hand will release you!)

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