Diadematoida

Common Names

Diadematoid sea urchins are commonly referred to as long-spined sea urchins due to their distinctive long, sharp spines. They are also known as diadems, pencil urchins, and crown-of-thorns starfish.

Characteristics

Diadematoid sea urchins possess a number of defining characteristics:

• Long, sharp spines: This is the most prominent feature, offering protection from predators and aiding in locomotion.
• Five-part radial symmetry: Like all echinoderms, they exhibit a pentameral body plan.
• Test: Their rigid, calcareous shell (test) is covered with spines and pedicellariae (small pincer-like structures).
• Tube feet: They have numerous tube feet, which are used for movement, feeding, and respiration.
• Aristotle's lantern: This complex jaw structure is used for scraping algae and other food from surfaces.

Environments

Diadematoid sea urchins inhabit a range of marine environments, including:

• Coral reefs: Many species thrive in coral reef ecosystems, playing an important role in maintaining coral health.
• Rocky shores: They can be found in intertidal zones and on rocky substrates.
• Seagrass beds: Some species graze on seagrass, contributing to the diversity of these habitats.
• Deep sea: Certain diadematoid species inhabit deep-sea environments.

References

For further information and resources on Diadematoida, refer to the following websites:

• World Register of Marine Species: https://www.marinespecies.org/aphia.php?p=taxdetails&id=1242
• Encyclopedia of Life: https://eol.org/pages/3334457/overview
• IUCN Red List: https://www.iucnredlist.org/search?query=Diadematoida