WATANABE, JEFFREY T.*; YOUNG, CRAIG M.: Expanding the niche by extending the proboscis: Feeding habits of southern oyster drills, Stramonita haemastoma (Gastropoda: Muricidae), on sabellariid worm reefs

Survival of predators depends in part on the abundance and availability of suitable prey. Finding habitats where specific prey occur is especially important for organisms with planktonic larvae that disperse and settle in a variety of habitats. On the east coast of Florida, larvae of the southern oyster drill, Stramonita haemastoma,often settle on sabellariid worm reefs constructed by the polychaete Phragmatopoma lapidosa, a habitat where oysters, the snail�s typical prey, are rare. On worm reefs, S. haemastoma feed on worms by inserting the proboscis deeply into sabellariid tubes. Worm-feeding snails have much longer proboscides than bivalve-feeding conspecifics, suggesting that the proboscis is phenotypically plastic. Whereas typical oyster drills must bore holes for days before encountering food, S. haemastoma on worm reefs can attack and consume their prey in 15-50 minutes. In the laboratory, worm predators consumed an average of 11 worms per week and preferred P.lapidosa prey over the oyster Crassostrea virginica. Despite tremendous savings of energy and time, and the opportunity to feed more often, S. haemastoma grow much more slowly on a diet of polychaetes than on oysters. Although S. haemastoma possess the ability and anatomy to expand their trophic niche, sabellariid worm reefs remain a marginal habitat for this species.