Preliminary observations on the usefulness of hinge structures for identification of bivalve larvae

Abstract

Difficulties associated with discrimination of bivalve larvae isolated from plankton samples have long hampered both applied and basic research efforts in estuarine and open coastal marine environments. The vast majority of practical barriers to identification of larval bivalves may be eliminated through routine optical microscopic examination of the hinge apparatus of disarticulated larval shells. Representative micrographs of various ontogenetic stages of larval hinge development are presented for 12 genera (Mytilus, Geukensia, Crassostrea, Placopecten. Argopecten. Mya, Spisula, Mulinia, Ensis, Arca, Arctica. and Mercenaria) from 9 bivalve superfamilies (Mytilacea, Ostreacea. Pectinacea, Myacea, Mactracea. Solenacea, Arcacea, Arcticacea. and Veneracea). The larval hinge apparatus (provinculum). by itself is generally useful for superfamilial separation. When coupled with a consideration of gross shell shape, detailed examination of hinge line structures often permits generic or even specific, identification. A format is suggested for organization of qualitative morphological life history data that will provide an adeqate basis for comparison of the larval stages of various species of bivalves.