The significance of contrasting feeding strategies on the reproductive cycle in two coexisting tellinacean bivalves

Semele solida and Tagelus (Tagelus) dombeii are two tellinacean bivalves which coexist in the lower intertidal zone of a sandflat in south-central Chile but follow different feeding strategies. Wheras T (T.) dombeii is a suspension-feeder, S. solida is a facultative deposit-feeder. In this study, digestive gland indices and reproductive cycles were described in relation to annual food availability and related to their feeding modes. Results showed that gonadic index cycles were similar for both species, with highest values being observed during the spring when water temperature was still on the rise and microflagellate and centric diatom density was at its peak. However, histological analyses indicated that the spawning period of T. (T.) dombeii extended from November 1995 to March 1996 and from August 1996 to January 1997, whereas S. solida presented a continuous spawning period that extended from September 1995 to December 1996. Results suggest that extended spawning throughout the winter by S. solida is a consequence of its ability to feed on bottom deposits when food in suspension is low.