Ophiuroidea Characters

Characters common to all Echinodermata

• They are all deuterostomes (the anus is developed before the mouth - only seen in echinoderms and chordates).
• They have no defined head or brain.
• Possess an endoskeleton (test) composed of porous calcium carbonate plates covered by a thin protoplasmic skin.
• Secondary radial symmetry, most with penta-radial symmetry.
• Unique to the phylum is the water vascular system (WVS) which functions for the locomotion (tube feet), respiration and feeding.
• Also unique to the phylum is a connective tissue called mutable collagenous tissue (MCT).
• Most echinoderms are covered in bumps and spines.
• All have the ability to regenerate parts of their body.
• Only found in steno-haline (true marine) environments, all types are free living.

Unique to Ophiuroidea

• All the viscera (internal organs) are contained within the central disc, the disc is well differentiated from the arms.
• The arms (generally 5) are long and sinuous, up to 60cm long used to “row” with for locomotion. This allows a faster movement within the water column.
• They have no anus, all food is taken in, and undigested food excreted, though the mouth. They cannot turn their stomachs inside out as seen in star fish.
• The tube feet do not have the suctorial ability of other echinoids, who use suction to move about slowly over surfaces and to prise open the shells of prey.

• Characters
• Anatomy
• Major subgroups
• Fossil record
• Modern forms
• Literature and web links
• Ophiuroidea home page

Author: Lorna O'Brien
Last updated: 19/11/2006
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