Discriminatory predation by three invertebrates on eastern oysters (Crassostrea virginica) compared with non-native Suminoe oysters (C. ariakensis)

Abstract. Diminished populations of eastern oysters Crassostrea virginica in Chesapeake Bay have stimulated proposals to introduce Crassostrea ariakensis from Asia to restore oyster stocks. As part of a program evaluating possible ramifications of such an introduction, we studied how invertebrate predators responded to this non-native oyster. We compared predation activity under laboratory conditions by oyster drills ( Urosalpinx cinerea; Eupleura caudata ) that bore through an oyster's shell and by the seastar Asterias forbesi that pulls shell valves apart. These three predators preyed significantly (p<0.05) more on the familiar C. virginica than on the novel C. ariakensis . We previously reported that five crab species preyed significantly more on C. ariakensis than on C. virginica , with predation by polyclad flatworms similar between oyster species. Thus, the drills and the seastar differed from the crabs and the flatworms in their response to novel prey. When Urosalpinx cinerea was placed in a Y-maze after being held for 40 d with oysters of one species or the other, the drills moved toward C. virginica effluent more than toward C. ariakensis effluent. This response did not depend on the species of oyster the drills had been held with, suggesting that the drills were responding to more familiar infochemicals from eastern oysters than from the non-native oysters.