Exploring marine mollusc drilling predation

Abstract

Predation marks by drilling molluscs serve as evidence for feeding activity and the selective pressure exerted by these organisms. This behaviour has been extensively studied to understand predator-prey relationships in both extinct and living species. The objective of this study is to characterise the mollusc drilling predation on gastropods from Playa Guardalavaca, Cuba, based on shell assemblages collected in the supralittoral thanatocoenosis. We examined the species richness and abundance of drilled and non-drilled shells and calculated predation rates. Additionally, we investigated the relationship between drilling predation and prey size in 11 species. To compare drilled and non-drilled shells, we used the median and interquartile range due to the asymmetric distribution of the measurements (tested with a two independent samples Wilcoxon test). Furthermore, we employed a Kolmogorov-Smirnov test to compare the size distribution frequencies of each species (drilled and non-drilled shells). A total of 114 gastropod morphospecies and nine species groups were identified, with the families Fissurellidae, Columbellidae, and Turridae exhibiting the highest species richness. Five species were identified as new records for the area. A total of 5,768 shells were quantified, out of which 1,411 displayed drillholes (24.5% prevalence). The most abundant species are not the most preyed upon, presenting a distinct pattern compared to bivalve assemblages in this and other locations. The highest predation rate was observed among individuals of medium size within each species. This pattern may be attributed to the predators' ability to manipulate their prey, potentially encountering difficulties in drilling into the harder, thicker shells of larger individuals. In contrast, smaller shells may not offer sufficient food resources, resulting in lower predation rates. Statistical analyses revealed significant differences in predation related to shell size for six out of the 11 tested species, as well as for the entire assemblage. Potential predators were identified, some of which exhibit drillholes themselves. In general, drilling predation in gastropods from the studied area appears to be influenced by a combination of factors, including high species richness of both predators and prey, prey abundance, specialised feeding strategies of predators, and habitat diversity. Received: 02.06.2023 Accepted: 12.12.2023

Keywords

• biotic interactions
• Caribbean Sea
• drillholes
• feeding behaviour
• Gastropoda
• Mollusca