The Predatory Echinoderm: Heart Urchin

What is the predatory echinoderm that lives and feeds below the sediment surface?

A) Brittle star B) Fiddler crab C) Heart urchin D) Sand crab E) Sand star

Final Answer:

The heart urchin

The heart urchin, or sea urchin, from class Echinoidea is the predatory echinoderm that lives and feeds below the sediment surface. They use five rows of tube feet for movement and primarily consume organic detritus. Echinoderms as a group, which includes sea stars and brittle stars, are known for their spiny skin and radial symmetry.

Explanation:

The predatory echinoderm that lives and feeds below the sediment surface is the heart urchin, also known as a type of sea urchin. Sea urchins are an example of the class Echinoidea. Unlike brittle stars (Ophiuroidea) or sand stars (Asteroidea), heart urchins are hemispherically shaped and utilize five rows of tube feet for slow movement through the sediment. While many of their echinoderm relatives are suspension feeders or predators, heart urchins primarily consume organic detritus - the fragmentary remains of other plants and animals.

Echinoderms are a group of marine organisms named for their spiny skin, with other members of the group including sea stars, sea cucumbers, and brittle stars. They are known for their radial symmetry and in some cases their ability to regenerate body parts due to their impressive powers of regeneration. However, heart urchins are distinguished by their unique, below-the-sediment lifestyle.