(^) Echinoderms have varied diets and feeding modes. Ophiuroids range over the
bottom – selecting detritus, ingesting sediment, filtering particles above the surface,
and even moving to deadfalls. Sea stars ingest sediment, prey on clams and other
animals of low motility, and in one group (Porcellanasteridae) filter water drawn
down into a subsurface burrow. Urchins are mostly deposit feeders, ingesting
sediment as they move over it. They do move to windrows or masses of detritus and
consume them rapidly. Some urchins that have evolved a bilateral symmetry live in
burrows and filter water pumped through by movement of their spines. Sea
cucumbers ingest sediment as they move across it, leaving tracks behind and
depositing fecal blobs modified by mucilage addition and partial digestion of organic
matter. Crinoids filter particles from the flow with specialized tube feet, passing the
catch to the mouth along the limbs in mucus strands.
(^) A few very large polychaetous Annelida perhaps qualify as megafauna, most of
them deep-sea scale worms in the family Polynoidae. Two other worm phyla include
large animals: the Hemichordata (including Enteropneusta) and Echiuroidea. These
live on or in the bottom, selecting particles from the surface with specialized cephalic
structures. Some hemichordates move in oscillating patterns, leaving characteristic
fecal traces. Echiurids sit in a burrow, casting their proboscides across the sediment in
ff
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