Sexual differentiation of the somatic gonad tissue in marine bivalve mollusks: esterase- and fibronectin-like recognition signals
Published: 1 June 2001
M Paz, A Mikhailov, M Torrado
Univ La Coruna, Inst Hlth Sci, Dev Biol Unit, La Coruna, Spain
Textbooks usually indicate that in many species sex determination starts with gonad differentiation, triggered during early embryonic development. Once a primary somatic gonad is formed, the gonad-derived inductive signals are used to maintain the sex differentiation of germ cells. In marine bivalves, sex is not determined until the germ cells are differentiated, whether that is in the larva or in the juvenile. As sex is often decided late in post-larval development, gonad differentiation starts in the adult state. It is generally accepted that bivalves have no great difficulty in transforming from hermaphroditism to gonochorism and vice versa (Mackie, 1984). Our results focus attention on the patterns of gene expression in the "common" gonad (i.e., ovotestis) of the simultaneous hermaphroditic scallop species, Pecten maximus, during maturation and reproduction periods. In this species, as in almost all marine bivalves, the connective-tissue cell types present in the testis and ovary of the "common" gonad are essentially identical. Using biochemical, immunochemical and molecular approaches, we demonstrate for the first time that the scallop ovotestis is characterized by germ-cell-associated somatic protein expression.