Sea Cucumbers

Description

Sea cucumbers are “spiny animals”, members of the phylum Echinodermata and relatives of the seastars and sea urchins. All echinoderms are marine and nearly all are bottom-dwellers. They are unique in having a 5-part body design and a water-vascular system of internal canals which provides hydraulic power for their many muscular tube feet.

Sea cucumbers differ from other echinoderms in having an elongate, cylindrical body with the mouth and anus at opposite ends. Because their body is muscular and soft rather than spiny, sea cucumbers are sometimes confused with sea slugs (snail relatives that lack a prominent shell). An easy way to tell them apart is to look for a head. Sea slugs, like snails, have a head with sensory tentacles. Sea cucumbers, like other echinoderms, lack a distinct “head”. Instead, the mouth end of a sea cucumber is ringed by 5 feeding tentacles used in gathering food particles. Sea cucumbers either gather detritus (bits of plant and animal matter) and bacteria from seafloor sediments or filter particles from the water.

Sea cucumbers lack some features common in other echinoderms. The 5-part body design you can see in seastars and even sea urchins is harder to find in many sea cucumbers. Some sea cucumbers have 5 rows of tube feet running the length of the body. But, in many sea cucumbers, you have to look internally to see the pattern — five muscle bands run the length of the body. A few sea cucumbers have 5 “teeth” around the anal opening. These “rump teeth” are not used in feeding, but may protect the cucumber from parasitic fish that shelter in the cucumber’s body.