Johnson's Sea Cucumber

Image from Monterey Bay Aqaurium

Sea urchins, sea cucumbers, and sand dollars are all part of the Phylum Echinodermata. These invertebrates are classified as echinoderms because of their endoskeletons, unique water vascular system, and radial symmetry as adult organisms. Sea urchins and sand dollars are members of the Class Echinoidea because their endoskeletons form round, rigid, shell-like tests with movable spines and pedicellariae (pincer-like organs that help keep the body clean). Sea cucumbers are classified as Holothuroidea because they are worm-like organisms that do not have spines and lack an obvious radial symmetry. Their feeding methods, locomotion and methods of reproduction make these organisms unique.