Paleozoic Gardens – Sea lilies, sea cucumbers and brittle stars

By Tom Shirley

Who’s a star in the deep sea?  Sea stars and their relatives. Other than the deep-sea corals, perhaps the most conspicuous and common animals of the deep are the echinoderms. These spiny-skinned animals include sea urchins, sea stars, sea cucumbers, sea lilies or crinoids, and brittle stars.

One easy way to recognize them is that their body parts occur in multiples of five. They also have a unique water vascular system that operates hydraulically to move tube feet, arms, etc., all with a minimum of energy. And their name (spiny-skin) gives yet another clue: many of them are covered with spines, such as the sea urchins. In the deep sea on level-bottom covered by mud and sand, the brittle stars are almost everywhere. Many extend three of their five arms into the current to catch food drifting by, while others ingest sediments to digest the smaller animals living within.

On rocks, corals and sponges, basket stars, with their thousands of arms filter the currents. Sea cucumbers are buried in the sediments, extending white tentacles in multiples of five into the current; these dazzlingly white tentacles grab your attention in every video. And almost everywhere a bit of hard substrate exists, the sea lilies abound, extending lacy arms to capture zooplankton. Most folks think of crinoids as relicts of the Paleozoic, gone with the dinosaurs, but in the deep sea, the crinoids still predominate.

The sea stars are less abundant, but are the true lions of the sea floor, the sea stars. These true symbols of the sea prey upon corals, sponges, clams, barnacles, and most any other animals who can’t escape. These beautiful, abundant and widespread animals of the deep sea have made their success without the benefit of anything resembling a brain: there’s hope for us all.