A Comparative Study of Some Features of the Biology of<i>Amphiura Filiformis</i>and<i>Amphiura Chiajei</i>[Ophiuroidea] Considered in Relation to their Distribution

Abstract

SUMMARY By comparing the two species of Amphiura in 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 filiformis holds 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 chiajei does 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 that Amphiura filiformis is a rapidly growing species with a high metabolic rate and food requirement, whereas Amphiura chiajei is slow growing and long-lived with a low metabolic rate. The environmental requirements of the two species are discussed.