21. It is infesting " Ophiocomina nigra ", the black brittle star , in the Firth of Clyde, Scotland. 22. It is a fast-growing brittle star and is not thought to live for more than three years. 23. Brittle stars of the genus " Ophiomastix " as well as shelled gastropods are also not attacked.24. Brittle stars are the most agile of the echinoderms, raising their discs and taking strides when moving.25. Sea urchins are close relatives of starfish, crinoids, brittle stars and sea cucumbers, all being echinoderms ('spiny skins'). 26. The smallest brittle stars found have just two segments per arm and a disc diameter of two millimetres. 27. In the Paleozoic era, brittle stars had open ambicular grooves, but in modern forms, these are turned inward. 28. In these starfish and brittle stars , direct development without passing through a bilateral larval stage usually takes place. 29. This brittle star usually metamorphose into young brittle stars which drift in the plankton for about three weeks before settling. 30. This brittle star usually metamorphose into young brittle stars which drift in the plankton for about three weeks before settling.
