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Size at first maturity, oocyte envelopes and external morphology of sperm in three species of Lucinidae (Mollusca: Bivalvia) from Florida Keys, USA.

Gonads in the tropical lucinid bivalves Ctena orbiculata, Codakia orbicularis and Lucina pensylvanica are situated in the cephalopodial mass, above the foot and behind the gills. Our age estimates for Lucina pensylvanica suggest that individuals less than one year old are immature, as in C. orbicularis, and that both males and females mature at two years. For Ctena orbiculata, we have no age data , but we consider that this species may also have early development. The mature individuals of the three species were spawning or in resorption. The water temperature reached 29-30şC during sampling dates, and most of the specimens collected were empty shells. Parasites were found in the digestive diverticula of C. orbiculata and L. pensylvanica. External ultrastructure of the spermatozoon shows differences between the three species. C. orbicularis and L. pensylvanica have a long-headed spermatozoa, while C. orbiculata has a middle size head. C. orbicularis posses an undulating membrane in the tail, the other two species lack of it.

bivalve; Lucinidae; maturity; sperm morphology

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