A Comparative Study of Some Features of the Biology ofAmphiura FiliformisandAmphiura Chiajei[Ophiuroidea] Considered in Relation to their Distribution

Abstract

SUMMARY: By comparing the two species ofAmphiurain controlled, directional bottom current flows, clear differences of behaviour can be demonstrated. These differences have been shown to be associated with two quite distinct feeding methods.Amphiura filiformisholds the arms up into the current flow with a rheotactic response to current direction and feeds by trapping both non-living particulate suspended matter and phytoplankton.Amphiura chiajeidoes not show this response and feeds exclusively on deposited matter on the sediment surface. Both species have modifications of the podia associated with the different methods of feeding. Estimates of growth rate, longevity and oxygen uptake suggest thatAmphiura filiformisis a rapidly growing species with a high metabolic rate and food requirement, whereasAmphiura chiajeiis slow growing and long-lived with a low metabolic rate. The environmental requirements of the two species are discussed.