Differences in tyrosine phosphorylation of oocyte key proteins during 5HT-induced meiosis reinitiation in two bivalve species.

The neurohormone serotonin (5HT) triggers meiosis reinitiation in oocytes of the pelecypod molluscs Spisula solidissima and Ruditapes philippinarum. However, while Spisula oocytes complete maturation, Ruditapes oocytes arrest in metaphase I. Anti-phosphotyrosine antibody revealed that serotonin triggered an early tyrosine phosphorylation of p42mapk which was transient in Spisula, but persisted in Ruditapes. Moreover, dephosphorylation of tyrosine residues of p34cdc2 was only observed in Spisula oocytes, simultaneously with germinal vesicle breakdown. The possibility is discussed that such differences may account for maintenance of the metaphase I block.