Alternative predation tactics of a tropical naticid gastropod

Aquarium observations of naticid gastropods from Hong Kong show that different species attack their bivalve prey in different ways. Natica gualteriana and Glossaulax didyma appeared always to use conventional modes of boring, i.e., through one shell valve, before consuming the prey, but some larger prey of C. didyma with incomplete borings were consumed after having apparently suffocated before boring was complete. In contrast, Polinices tumidus prey may be side-bored, edge-bored (i.e., through the commisure of the valves) or suffocated and consumed without boring. The frequency of each of these modes of attack vary with different prey species. Non-boring predation, in aquarium experiments, accounted for 14.7–54.9% of attacks with different species of prey. Suffocated prey were found to be enwrapped in a thick, viscous coat of mucus, which in partially consumed prey showed a round hole overlying the ventral shell gape marking the entrance hole made by the proboscis. The observations reveal considerable flexibility in predation behaviour in this tropical naticid and have important implications in the interpretation of naticid predation rates in recent and fossil dead shell assemblages.