Observations on the biology of the Veined Rapa whelk, Rapana venosa (Valenciennes, 1846) in the Chesapeake Bay

The recent discovery of the Veined Rapa whelk (Rapana venosa, Valenciennes, 1846) in the lower Chesapeake Bay provides an opportunity to observe the i nitial biological and ecological consequences of a novel bioinvasion. These large predatory gastropods occur in subtidal, hard bottom habitats in the lower Bay and are capable of feeding, mating, and moving while completely b urrowed. Hard clams (Mercenaria mercenaria) are consumed preferentially in the laboratory when offered concurrently with oysters (Crassostrea virginic a), soft clams (Mya arenaria), and mussels (Mytilus edulis). Chesapeake Bay R. venosa readily open and consume large hard clams (30 to 85 mm SH) leavi ng no visible signs of either drilling or boring behavior. Shell morphology and thickness may provide an inherent size-selective predation refuge for Rapa whelks in the Bay. These same shell characteristics may change the dyn amics of shell selection by local hermit crabs, particularly the striped he rmit crab, Clibanarius vittatus. Recent collections of striped hermit crabs from the Hampton Roads area indicate that very large striped hermit crabs are using empty Rapana shells as shelters.