Edge-drilling behavior in the predatory gastropod Notocochlis unifasciata (Lamarck, 1822) (Caenogastropoda, Naticidae) from the Pacific coast of Panama: taxonomic and biogeographical implications

We conducted a laboratory study to determine drillhole siteselectivity patterns in the predatory behavior of Notocochlis unifasciata (Lamarck, 1822), which is a common naticid gastropod on the eastern Pacific coast of Central America, preying on two infaunal venerid bivalves – the thin-shelled and weakly ornamented Leukoma grata (Say, 1831) and the thick-shelled and strongly ornamented Iliochione subrugosa (Wood, 1828). Spatial patterns of drillhole distribution indicate strong preferences for drilling the umbonal region and the ventral edge of the shell, with the proportion of edge- to wall-drilling attacks increasing in thicker, strongly ornamented prey that were larger than their predator’s own size. Drilling patterns from museum and beach samples of I. subrugosa collected across the geographic range of N. unifasciata (Panama to Costa Rica) were consistent with laboratory findings. Review of the confirmed cases of edge-drilling behavior by other naticids indicates that this study is the first confirmed report of the behavior in the naticid subfamily Naticinae. In light of these findings, we discuss hypotheses on the geography and ecology of edge-drilling predation by subtropical and tropical naticids to guide future research.