Shape differences among boreholes drilled by three species of naticid gastropods

Abstract

Naticid gastropods leave a record of predation in the form of characteristic countersunk circular boreholes. We fed bivalve prey to naticids to test whether the ratio between the inner and outer borehole diameter differed among three Recent naticid species: Euspira heros, E. lewisii and Neverita duplicata. Fossil shells from a Miocene-aged assemblage, containing naticids previously identified as E. heros and N. duplicata, were also included in our analyses. Ratios of the inner to outer diameters of naticid boreholes in bivalve shells showed that there were significant differences in borehole shape between E. heros and the two other Recent species. We found no significant differences between the ratios of E. lewisii and N. duplicata; however, a principal component analysis showed that boreholes distinctly cluster according to species. The Miocene boreholes were also distinct from the Recent, indicating that the Miocene naticids may be a separate species from E. heros and N. duplicata. We have shown that there is a species-specific component to borehole geometry. This may have important implications for palaeobiological studies, because the index of borehole functionality, previously described as an inner to outer borehole ratio of 0.5 for all naticids, may differ between species. © The Author 2003. Published by Oxford University Studies on behalf of The Malacological Society of London, all rights reserved.