TEMPORAL AND SPATIAL TRENDS IN MURICID AND NATICID GASTROPOD PREDATION ON CREPIDULA IN THE U.S. COASTAL PLAIN

A comprehensive survey of drilling predation by naticid and muricid gastropods on prey species belonging to the gastropod genus Crepidula was conducted for Plio-Pleistocene mollusc assemblages from the Atlantic Coastal Plain of Virginia, North Carolina and South Carolina, and from the Atlantic and Gulf Coastal Plain of Florida. Muricid and naticid drilling frequencies from formations in Virginia, North Carolina, and South Carolina steadily decreased from the middle Pliocene to the late Pliocene and then rose significantly into the Pleistocene, following the Plio-Pleistocene mass extinction. This pattern is similar to that observed in an assemblage-level survey of naticid gastropod predation on Cretaceous through Pleistocene Coastal Plain mollusks conducted by Kelley and Hansen. Muricid drilling frequencies on Crepidula fornicata were inversely correlated with prey effectiveness (the ratio of incomplete drillholes to total attempted drillholes). During times when muricid drilling frequencies (representing successful predation) were low, C. fornicata specimens exhibited many incomplete drillholes, possibly due to the prey’s ability to physically defend itself from drilling gastropod predators. Muricids and naticids were highly selective with respect to drillhole site on the prey’s shell for Pliocene and Pleistocene samples from Virginia, North Carolina, and South Carolina. Pliocene samples from Florida showed that muricids were also selective with respect to drillhole site on the prey’s shell; however, the preferred drillhole site for muricids from Florida was different from that shown in Pliocene samples from Virginia, North Carolina, and South Carolina.