DEATH IN PARADISE: MULTI-YEAR RECORDS OF PREDATION ON THE BAHAMIAN ECHINOID LEODIA

The irregular echinoid Leodia sexiesperforata is widespread and locally abundant in the Caribbean. In the modern, this infaunal sand dollar inhabits soft sediments and typically occurs in small, but densely populated patches. These local populations generally experience high predation 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. This predatory interaction may result in high mortality of sand dollar populations. Although there have been a number of studies dealing with predation on echinoids, we are lacking long-term studies necessary for estimating variability in predator-prey dynamics.

In this study, we analyzed multi-year trends in predator-prey interactions between the carnivorous snail Cassis tuberosa and the sand dollar Leodia sexiesperforata in the Bahamas (San Salvador Island). Over a five-year period (2010, 2013, 2014, 2015, and 2017), we recovered 241 denuded tests of Leodia sexiesperforata from Sand Dollar Beach. Results indicate very high drilling frequency (>90% tests drilled), with relatively consistent rates of predatory attacks over the years: 2010: 82% (N=67); 2013: 100% (N=14); 2014: 98% (N=54), 2015: 85% (N=27); and 2017: 100% (N=134). In addition, drilling patterns indicate that Cassis tuberosa shows a high preference for the oral side of the test. A number of factors may contribute to site selectivity by gastropod predators, such as specific attack or grappling methods, targeting locations on the test that are easier to penetrate, or access to high energetic value tissues. The overall results suggest that predation by cassids may be a persistent source of mortality and can produce an identifiable fossil record of these intense predator-prey interactions.