G. Martinez
Abstract:
The spawning is a very important process in the life of animals. In bivalve molluscs this process is regulated through the interaction of both exogenous as endogenous factors. Among exogenous factors are temperature, salinity, pH, levels of dissolved oxygen, presence of food, mechanical stresses, and lunar phase. The role of these exogenous factors has been extensively investigated but less research has been devoted to endogenous factors. Among endogenous factors, prostaglandins and some amines, produced by nervous cells, are considered to play an important role.
A great deal of research on this subject has been referred to the induction of spawning by homogenates of nervous tissue or by monoamines which are a common secretion product of that tissue. Serotonin has been shown to be one of the most effective spawning inducers although the response of bivalves to it varies according the specific reproductive characteristics of the species. For example, in the case of gonochoric pectinids, the sensitivity of male to this amine is considerably higher than that of the female individuals. In the case of hermaphrodite scallops, 5HT has been effective inducing release of sperm but not of oocytes. On the other hand, the study of endogenous factors controlling spawning, has been focused on identifying the presence of monoamines and analyse the quantitative variations of them during spawning.
Another group of compounds that has been investigated is that of the prostaglandins. This research has been focused from different points of view. Inhibitors of their synthesis have been used to study the effect on spawning, the variations in their levels during the spawning have been investigated and also the inductive effects on the release of gametes.
We shall review all these aspects in this presentation, focusing mainly on the research about the endogenous factors.
(Department of Marine Biology, Universidad Catolica del Norte, Coquimbo, Chile)