Ophiuroidea

Ophiuroidea is a large class of Echinoderms containing over 2,000 species. Also known as brittle stars or basket stars, they are closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens. They are also known for their ability to regenerate lost arms and for their bioluminescence.

Anatomy

The central body disc of Ophiuroidea is sharply marked off from the arms. The disc contains the internal organs, while the arms have only muscles and nerves. The mouth is located on the underside of the disc. The skin has hard, calcified plates and spines, which form a rigid armor.

Behavior and reproduction

Ophiuroidea are known for their evasive behavior. They move quickly when disturbed, and can detach arms to distract predators. The detached arm continues to move, drawing the predator's attention away from the escaping brittle star. They are also capable of regenerating lost arms.

Reproduction can be both sexual and asexual. They have separate sexes and fertilization is usually external, but some species carry their young inside their bodies until they are fully developed.

Ecology

Ophiuroidea are found in all of the world's oceans, from the tropics to the polar regions. They live in a variety of habitats, from the intertidal zone to the abyssal depths. Some species are suspension feeders, while others are scavengers or predators.

Taxonomy

The class Ophiuroidea is divided into two orders, Ophiurida and Euryalida. The former includes the brittle stars, while the latter includes the basket stars.

See also

• Echinoderm
• Starfish
• Ophiurida
• Euryalida

References

Ophiuroidea Resources
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