Drilling predation on the clypeasteroid echinoidEchinocyamus pusillusfrom the Mediterranean Sea (Giglio, Italy)

Drilling predation of cassid gastropods (tonnacean) on echinoids is common in marine environments but is rarely documented. Tests of the minute clypeasteroid Echinocyamus pusillus OF Muller (1776) were collected from the Mediterranean Sea (Isola del Giglio, Italy). Besides general morphology, features pertaining to the morphology and distribution of predatory boreholes were examined. Furthermore, borehole frequencies among different samples sites were compared. Cassid gastropods are assumed to be the originators of the boreholes. A total of 1061 tests were analysed for drilling rates with 15.3% drilled with predominantly single boreholes. The borehole morphology is strongly affected by the microstructure of the skeleton; the borehole outline is irregular if drilled within areas where ambulacral pores are present. Vertical borehole morphology is influenced by stereom density. The size frequencies of non-drilled and drilled specimens show significant differences. Comparisons of borehole size with test size ...