Gray, 1840
The adult body of Ophiuroidea (brittle stars and basket stars) is stellate with five unbranched or branched articulated arms; the arms are clearly set off from the central disc (in contrast to the sea stars [Class Asteroidea]). Adults are benthic.
The pluteus larva [Ophioruidea pluteus ] is pelagic. The larval arms are typically set in a more or lass flat plane, by which it is distinguished from pluteus larvae of sea urchins [Class Echinoidea]. The larval arms are spine-like and internally enforced with a skeletal structure.
The larval stage of the brittle star Ophiothrix fragilis (common in the North Sea) lasts for 11 to 30 days. The larvae metamorphose into juvenile brittle stars whilst still in the plankton.
Spawning of Ophiothrix fragilis occurs from July to September (October), in some cases even from May to january, all depending on local circumstances. It appears as if O. fragilis has a long breeding season, with peak activities in summer/autumn. The larval body is globose and its size is 0.1-0.3 mm, but the overall size including the "arms" (or spines) ranges from 1 to 2 mm. The larva is a suspension feeder.
Ophiopluteus larvae are recognised in the key, but not identified to species.