Plesiastreidae
Plesiastreidae is a family of sea urchins in the order Diadematoida. It is comprised of a single genus, Plesiaster, with two recognized species. These sea urchins are characterized by their distinctive, flattened bodies and relatively short spines. They are found in the Indo-Pacific region, inhabiting rocky reefs and coral rubble. Plesiastreids are important members of their ecosystems, contributing to the health of coral reefs through their grazing activities.
Common Names
Plesiastreids are often referred to as "flat sea urchins" due to their unique flattened shape. However, they do not have widely recognized common names outside of scientific circles.
Characteristics
Plesiastreids exhibit several defining characteristics that distinguish them from other sea urchin families. They are characterized by:
- Flattened body shape: Unlike many other sea urchins, Plesiastreids possess a flattened body that allows them to cling to surfaces and navigate in tight spaces.
- Short spines: The spines of Plesiastreids are relatively short compared to other sea urchin species, providing them with a distinctive appearance.
- Absence of pedicellariae: Pedicellariae are small, pincer-like structures found on the surface of many sea urchins, but they are absent in Plesiastreids.
Environment
Plesiastreids are found in the Indo-Pacific region, primarily in tropical and subtropical waters. They inhabit rocky reefs, coral rubble, and other hard substrata. Their flattened bodies allow them to effectively navigate these environments, seeking out algae and other food sources.