Foraging Behaviors of Hexaplex trunculus (Gastropoda: Muricidae) Juveniles

Foraging behaviors of juvenile Hexaplex trunculus (Linnaeus, 1758), a predatory snail, preying on the Mediterranean mussel Mytilus galloprovincialis were investigated. To understand the mechanisms of the prey-predator relationship between young forms of these species and assess the foraging capabilities of the snails, size selection and attacktype experiments were set up. Furthermore, the predation signatures, which are used as a valuable tool for ecology and paleoecology studies, were measured with an alternative method; their locations were classified and related with the predator-prey sizes to make some descriptions. Snails (as two size categories, about 2-6 and 6-11 mm shell length (SL) during the experimental period) typically accessed the mussel (as four size categories up to 20 mm SL) flesh by drilling and/or marginal chipping. About 90% of the shell samples had at least one attack signature from each attack type. By the end of the experimental period, 74% of all of the attacks with the visible predation signature were made by drilling and 26% by chipping; attack type did not differ according to predator or prey size. Group-attacking events were observed frequently during the experiments as well as solitary attacks; 48% of the mussel shells that had at least one attack signature had multiple attack signatures. Positions of the drill holes were dense over anterior-dorsal areas and their distributions did not differ according to snail size. Drill hole diameters were found to be related with snail and also mussel sizes by linear regression. Even though both small and large juvenile snails were capable of foraging on mussels that were three or four times larger than themselves, they showed size preference for particular mussel size classes. The ratio of the prey size/predator size did not have any effect on the attack type of the snails. After reaching 9 mm (auxiliary experiments), snails started to consume larger mussels (more than 40 mm) as well as the individuals from smaller groups