Drilling predation on bivalve shell assemblages at Playa Guardalavaca, Cuba

Drilling predation plays an important role in the evolution and diversification of organisms, and is one of the most studied biotic interactions in fossil and modern records. Marks of drilling predation on mollusc shells are proof of food activity and the selective pressure of one taxon on another. In this study, we explore drilling predation on preserved bivalve death assemblages (thanatocoenosis) at Playa Guardalavaca, Cuba. We characterize the taxonomic composition, relative abundance and incidence of drilling. Furthermore, geometric morphometric tools were used to test whether there was a preference for any particular form of shell. Forty-eight species were identified, and a little less than half (21) showed drilling predation marks. The families with the highest species richness were Lucinidae and Tellinidae, with 11 species each. A total of 1,726 valves were quantified, estimating an abundance of 863 specimens. 190 valves showed drilling marks (22% of the abundance). The most abundant species were Lucina sp. (464 shells), Divalinga quadrisulcata (328), Americardia media (242), Ctena imbricatula (156), and Chione spp. (117). However, the most predated species were Epicodakia sp. (100%), Acorylus gouldii (56%), and Eurytellina sp. (44%). The highest predation rate occurs on small and medium-sized valves (≤ 7 mm); however, according to the Kolmogorov-Smirnov test, this result is only statistically significative in Lucina sp. (p < 0.001). The morphometric analysis showed predation preferences for species with semi-circular rather than elliptical shells. These results elucidate that drilling predation on bivalves is not only determined by the abundance of prey, but also by their external morphology and size, suggesting highly specialised feeding behaviour by predators.