Pre-Ingestive Feeding Behaviors of Two Sub-Tropical Bivalves (Pinctada Imbricata and Arca Zebra): Responses to an Acute Increase in Suspended Sediment Concentration

In laboratory experiments we examined the pre-ingestive feeding responses of two species of sub-tropical bivalves, the turkey wing Area zebra (Swainson) and the Atlantic pearl-oyster Pinetada imbrieata Röding, to an acute increase in natural suspended sediment concentration. These two sympatric species inhabit coastal regions of Bermuda and possess fundamentally different gill structures. Our simulated resuspension event caused a four fold increase in the concentration of suspended particles, which induced a significant decrease in clearance rates and a significant increase in the rate of pseudofeces production in both species. P. imbrieata indiscriminately rejected material in the pseudofeces, thereby moderating ingestion rate through bulk rejection. Specimens of A. zebra, however, demonstrated particle selection, rejecting material with significantly higher carbon and lower nitrogen concentrations, thereby increasing the quality of material ingested by approximately 31%. Our results indicate that sympatric species of bivalves can exhibit different pre-ingestive feeding behaviors when exposed to the same increase in suspended sediment concentration. Such interspecific comparisons are critical for the development of more explicit numeric models of physiological compensations of bivalves to environmental change.