Meeting Abstract

61.5  Saturday, Jan. 5  Mucus-net feeding behavior by Olivella semistriata, an intertidal snail on sandy beaches MCPHERSON, D.R.; SUNY at Geneseo mcpherso@geneseo.edu

Olivella semistriata is a prosobranch gastropod mollusc in the family Olividae, and it is abundant on gently sloping sandy beaches along the Pacific coast of Central America. These snails live in the intertidal zone and position themselves near the upper edge of the swash zone, where they bury themselves just beneath the substrate surface. They remain buried during the inward swash of the surf and also during most of the backwash. During a period of gentle flow near the end of the backwash they protrude their heads from the sand and extend a pair of tentacles, each of which bears a delicate mucus net. Each net then acts as a sieve to capture suspended material from the retreating water current. Mucus-net feeding behavior has been described in other gastropods, but the behavior observed in Olivella semistriata is distinct and unusual. I use video recordings to analyze the kinematics of the behavior and to determine the flow velocities at which mucus-net feeding occurs. The timing of head extension is highly synchronized among individuals and implies a high sensitivity to water flow velocity, which seems to be sensed from beneath the substrate surface. In addition to their unusual feeding behavior, these snails migrate up and down the slope of the beach with the tide, allowing individuals to continue mucus-net feeding throughout the tidal cycle. For this migration on the falling tide, snails emerge from the sand while the outflow is more substantial, and extend their metapodia as sails to capture the larger water currents. An analogous behavior occurs for migration on the rising tide. These behaviors are also highly synchronized among individuals and imply the presence of a �circatidal� clock circuit in the central nervous system.