Echinothuriidae

The Echinothuriidae are a family of sea urchins in the order Echinothurioida. They are distinguished by their distinctive, often brightly colored, and usually very fragile tests, the hard, protective outer shell of a sea urchin. These sea urchins are widely distributed in tropical and subtropical waters around the world.

Fire Urchin, Variable Fire Urchin – Asthenosoma varium

Common Names

Echinothuriids are commonly known as "spiny sea urchins" or "crown-of-thorns sea urchins", although the latter name is more specifically used for members of the genus Acanthaster, which is not part of the Echinothuriidae family.

Characteristics

Echinothuriids exhibit several key characteristics that set them apart from other sea urchins:

  • Test Structure: Their tests are often thin and porous, making them quite fragile. This structure is reinforced by numerous spines, which are usually long, slender, and hollow.
  • Coloration: Echinothuriids are often brightly colored, with hues of red, orange, yellow, or purple. This coloration can serve as camouflage or as a warning to potential predators.
  • Feeding Habits: Echinothuriids are primarily herbivorous, feeding on algae and detritus. They use their spines to scrape food off surfaces and transport it to their mouths.
  • Defensive Mechanisms: Their spines are often tipped with venomous barbs, which they use to defend themselves against predators. Some species also release a toxic substance called echinotoxin.

Environment

Echinothuriids are found in a variety of marine environments, including:

  • Coral reefs: Many species inhabit coral reefs, where they graze on algae and play a role in maintaining the health of the reef ecosystem.
  • Rocky shores: Some species can be found on rocky shores, often in areas with strong currents or wave action.
  • Deep sea: A few species are adapted to living in the deep sea, where they can be found at depths of several thousand meters.

References

For more information on Echinothuriidae, refer to the following websites: