Larval morphometrics and influence of adults on settlement in the gregarious ophiuroid Ophiothrix fragilis (Echinodermata). Biol Bull 208:92–9

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Marine Biological Laboratory is collaborating with JSTOR to digitize, preserve and extend access to Biological Bulletin. http://www.jstor.org Abstract. The development of Ophiothrix fragilis was documented using light microscopy, and the allometry of larval growth was quantified. Larval development to the suspended juvenile stage took 21 days under conditions that were probably optimal compared to those in the plankton. Larval shape changed through development as the larval body and arms grew. Growth of the posterolateral larval arms was continuous throughout development, even during metamorphosis when the larva became endotrophic. During this period, these larval arms function as locomotory organs, and their continuous growth is probably essential to support the juvenile as it increases in density through development of its calcareous plates. In induction assays using adult conspecifics, initiation of metamorphosis was spontaneous. Release of the posterolateral arms was induced by the presence of adults. This response is likely to enhance a juvenile's chance of recruiting to a suitable habitat in the Ophiothrix fragilis beds of the North Sea