Holothuria mexicana Ludwig, 1875 - donkey dung sea cucumber (center) & Oreaster reticulatus (Linnaeus, 1758) - reticulated starfish (left & right) from rocky shore intertidal zone. (photo taken by Lee & Mary Ellen St. John)

Holothurians (sea cucumbers) are bizarre animals. They lack the obvious pentaradial symmetry of other echinoderms (starfish, sand dollars, etc.). They have soft, elongated, flexible bodies. Their skeletons consist of numerous, tiny, calcareous sclerites embedded in the body wall or covering the outer surface of the body. In general, sea cucumbers are benthic and vagrant, slowly moving around on the seafloor. They use mucus to collect organic debris from the seafloor and then consume the debris-covered mucus. Some holothurians can discharge internal organs and toxins from their posterior in response to potential predators. Rough handling of sea cucumbers by people can result in the same discharge behavior.

Classification: Animalia, Echinodermata, Holothuroidea, Aspidochirotida, Holothuriidae