The Biological Bulletin, Vol 180, Issue 1 93-102, Copyright © 1991 by Marine Biological Laboratory

ECOLOGY AND EVOLUTION

The Effects of Flow on Polyp-Level Prey Capture in an Octocoral, Alcyonium siderium

M. R. Patterson
Division of Environmental Studies, University of California, Davis, California 95616

Particle capture by individual polyps and tentacles of the octocoral, Alcyonium siderium, was investigated in flows of different speed and turbulence intensity. In low flow (Umean = 2.7 cm/s; u' = 1.2 cm/s, where u' is the root mean square of the fluctuations from Umean), tentacles on the upstream side of a polyp capture the most prey. In intermediate flow (Umean = 12.2 cm/s; u' = 6.0 cm/s), downstream tentacles within a polyp catch the most prey. In high flow (Umean = 19.8 cm/s; u'= 4.0 cm/s), polyps are bent downstream, eddies form over the tentacular surfaces, and the capture distribution over tentacles becomes radially symmetric. At all flow speeds tested, particles are caught with increasing frequency nearer the tip of the tentacle relative to locations near the pharynx. At the highest flow speed tested, no particles are caught on the segment of each tentacle closest to the pharynx. The per polyp capture efficiency is low and drops markedly with increasing Reynolds number. The capture mechanism for this species appears to be direct interception; inertial impaction is shown to be unimportant. Flow modulation of particle capture by polyps is probably a general phenomenon among octocorals.

This article has been cited by other articles:

				M. C. Pratt Living where the flow is right: How flow affects feeding in bryozoans Integr. Comp. Biol., June 21, 2008; (2008) icn052v1. [Abstract] [Full Text] [PDF]