The Echinoid Directory


Echinoids can feed in a variety of different ways. Regular echinoids feed primarily using their lantern to bite and rasp. Many shallow-water forms are almost exclusively algivores, feeding on seaweeds, grasses and encrusting algae. Others are more generalist, feeding on sessile organisms, carrion and detritus on the sea floor. Echinostrephus, a rock-boring species, is dependent upon catching drift algae that passes across the mouth of its burrow. Little is known about the diet of deep-sea regular echinoids but they are presumably broad generalists and carnivores on sluggish or sessile organisms.

Irregular echinoids are primarily deposit feeders, living on the fine organic material that settles to the sea floor. Cassiduloids appear to be bulk sediment swallowers, rather unselectively passing large volumes of sediment through their gut for the small amount of organic material it contains. Sand dollars are more efficient, sieving the thin surface layer of sand for its fine organic particles using their aboral spines. Spatangoids and holasteroids both use oral tube-feet to selectively pick up organic detritus from the sea floor. Their tube-feet are specially modified and end in a mass of tiny sticky fingers that are efficient at picking up fine material. Some deep-sea holasteroids, like Echinosigra pictured above, are structurally modified to funnel flocculated organic material from the sea floor directly into their mouth.

See Jangoux, M. and Lawrence, J. M. 1982. Echinoid Nutrition. A. A. Balkema, Rotterdam.