Predation on two brachiopods, Joania cordata and Argyrotheca cuneata, from an offshore reef in the Tyrrhenian Sea

Abstract

Predator holes in empty shells of Joania cordata and Argyrotheca cuneata (Brachiopoda: Megathyrididae) collected in the marine protected area “Secche di Tor Paterno”, central Tyrrhenian Sea, Italy (41°35′N–12°20′E, at depths of 20–28 m), were analyzed. Predation intensity was low but appreciable, with the more common species J. cordata preyed on more frequently (6.7 %) than A. cuneata (3.8 %). Three main types of holes were recognized: (1) cylindrical drill holes with a circular outline, (2) larger irregular holes with a jagged outline, and (3) small holes at the bottom of depressions in the shell. They were probably produced by muricid gastropods, crabs, and Foraminifera, respectively. The large, irregular holes were the most common type in both brachiopod species. Evidence for predator selectivity with respect to which valve, the position of the hole on the valve, and the size of the brachiopod with respect to those available was assessed. The ventral valve, the postero-medial portions of both valves, and larger (J. cordata) or medium-sized (A. cuneata) shells were more frequently holed.