Damage to the eyes of the bivalve Chlamys opercularis caused by the ciliate Licnophora auerbachii

Abstract

The majority of specimens of the scallop Chlamys opercularis found in Strangford Lough, County Down, Ireland, are infected with a rare and exotic ciliate Licnophora auerbachii. The ciliate is found predominantly on the eyes of the scallop which (together with numerous tentacles) are borne by the middle marginal folds of the mantle. The ciliates are found attached to both the clear cornea covering the lens and also the surrounding pigmented iris, their large food vacuoles often containing black consistently sized granules, particles derived from the pigmented epithelial cells of the scallop eye. These cells are abraded from the surface of the iris and become detached due to the action of the basal disc of L. auerbachii during its clamping and locomotory activities on the eye surface. Scanning electron microscope observations show that the foot region of the ciliate exerts both a suction and abrasive action on the eye and leaves a distinct “footprint” on the eye surface in the form of a saucer-shaped depression. In many of the heavily infected scallops there was evidence of damage to the eyes with consequent loss of pigment and in some instances surface distortion of the eye itself.