Echinozoa

sea cucumber

While feeding, this sea cucumber sequentially folds up its tentacles and thrusts an arm into the mouth to lick off entrapped plankton.

Poriferous zone Stomopneustes variolaris test

Aboral (top) surface of purple urchin showing anus surrounded by spines, pinchers, and tube feet.

Closeup showing the urchin's chewing apparatus, 'Aristotle's lantern.'

Skeleton of purple urchin shows convex points of attachment of spines and openings for branches of the water vascular system that serve the tube feet.

Depth 24 m. For about two years, purple urchins denuded a localized patch of sea floor at moderate depth. We do not know why the sea otter did not prevent this localized catastrophe.

Porifera, Nudibranch?