MULTI-YEAR RECORDS OF PREDATION ON THE BAHAMIAN SAND DOLLAR LEODIA SEXIESPERFORATA

The infaunal echinoid Leodia sexiesperforata is a common bottom dwelling sand dollar that inhabits soft sediments throughout the Caribbean region. Local populations can experience high predatory pressure and are often preyed upon by carnivorous cassid snails. With the aid of their radula and acidic fluids, these snails drill holes into the tests of sand dollars and feed on internal soft tissues thereby leaving behind characteristic traces in the echinoid’s test. Although there have been numerous studies dealing with predation on echinoids, long-term studies focused on estimating variability in predator-prey dynamics are critically lacking.

In this study, multi-year trends in predator-prey interactions between the carnivorous snail Cassis tuberosa and the sand dollar L. sexiesperforata have been analyzed from the Bahamas (San Salvador Island). Over a period of nine years, denuded tests of L. sexiesperforata from Sand Dollar Beach were collected during sampling trips conducted in 2010, 2013, 2014, 2015, 2017, and 2019. Results indicate very high drilling frequency (>90% tests drilled), with relatively consistent rates of predatory attacks across all years of sampling, ranging from 80% (2010) to 100% (2013, 2017). In addition, drilling patterns indicate that C. tuberosa shows a high preference for drilling the oral side of the test. Many factors may contribute to site selectivity by gastropod predators, such as the cassid’s mode of attack and drilling methods, targeting test locations that are easier to penetrate, or access to more nutritious tissues. Results suggest that drilling predation by cassids may be a persistent source of mortality and may produce an identifiable fossil record of these intense predator-prey interactions.