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Sea cucumbers belong to Echinodermata, a large phylum of marine animals that includes sea urchins, brittle stars, sea stars, sea lilies and sand dollars. All are radially symmetrical, although in some groups, such as the Class Holothuroidea, to which the sea cucumber belongs, this trait is sometimes difficult to identify. Holothuroids such as sea cucumbers are not plants, nor do they closely resemble their terrestrial namesake except in general form. Most have somewhat elongated bodies with an axis that runs from the animal’s mouth to its anal end. Some species have five obvious longitudinal rows of tube feet equally spaced around the animal’s circumference; however, since their bodies must lie with one side on the substrate, many have developed tube feet on the three rows that come in contact with the substrate, while the other two rows are either missing or reduced. In this case the sea cucumber appears bilaterally, rather than radially, symmetrical. A sea cucumber’s mouth is ringed with a row of fingerlike, stalked or branched tentacles, which are actually modified tube feet and part of the body’s water vascular system and are used for feeding. Unlike other echinoderms, whose fluid vascular systems are full of sea water, holothuroids contain body fluid. Two kinds of sea cucumber are common to the higher salinity waters of the lower Chesapeake Bay: the hairy, or common sea cucumber, Sclerodactyla briareus, also classified as Thyone briareus, and, less common, the pale sea cucumber, Cucumaria pulcherrima.
The hairy cucumber is a common holothuroid that occurs in shallow waters along the east coast of North America from Massachusetts and south to Florida and the Gulf of Mexico. Its body is about 4 ¾ long, 2 inches wide, and resembles the shape of a sweet potato. It looks a little like a hairy stone. Its surface can range in color from black and brown, to green or purplish. Sea cucumbers that occur in the Bay are usually brown. Their bodies are thickest in the middle; the mouth and anal ends are curved upward and are covered with fine tubular feet. The sea cucumber also has 10 large, branchlike tentacles around its mouth, which it can retract within its body. It uses its tube feet to creep along the substrate or to build up sediment around itself, leaving only its mouth and anal opening exposed. The tentacles sweep food particles into the mouth. If a sea cucumber is picked up or otherwise disturbed, it will (like a sea squirt) expel water from the rear opening, and if the disturbance is intense it performs an even more surprising move, even expelling some of their internal parts, which may sometimes—not always—results in the death of the animal. On the positive side, if an animal loses a tentacle, it can regenerate another in about three weeks. In the Bay sea cucumbers are found in higher salinity waters, on muddy or sandy bottoms, from the low-tide line to 20 feet deep.
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