Regulation of seasonal reproduction in mollusks

Understanding the physiological basis of environmental regulation of reprod uction at the cellular level has been difficult or unfeasible in vertebrate species because of the highly complex and diffuse nature of vertebrate neu roendocrine systems. This is not the case with the simple nervous system of mollusks in which reproductive neuroendocrine cells are often readily iden tifiable in living tissue. Given that there are mollusks that are seasonal breeders, that the neuroendocrine cells controlling reproduction have been identified in several molluskan species, that these neurons are conducive t o cell physiological analysis, and that basic features of cell biology have been highly conserved between mammals and mollusks, it seems that the moll usk would provide an excellent model system to investigate cell-physiologic al events that mediate effects of environmental signals on reproduction. Th e purpose of this review is to explore this idea in three species in which the topic of the neural basis of seasonal reproduction has been studied: th e giant garden slug Limax maximus, the freshwater pond snail Lymnaea stagna lis, and the marine snail Aplysia californica.