The effects of mating on the fine structure of neurosecretory caudodorsal cells in Helisoma duryi (Mollusca)

Abstract

The hermaphroditic snail Helisoma duryi does not lay eggs if raised as a virgin in isolation or when castrated. The fine structure of its neurosecretory caudodorsal cells (CDC), which produce the putative egg-laying hormone, was studied in reproductively inactive virgin and castrated snails and compared with that of the reproductively active mated snails, using electron microscopy, tannic acid incubation technique, and electron microscope autoradiography after injection of [3H]leucine. The CDC of virgin and castrated snails accumulate large numbers of elementary granules and appear synthetically inactive, whereas the CDC of mated snails contain fewer elementary granules and possess features characteristic of increased protein synthesis. The flattened cisternae of the rough endoplasmic reticulum of the CDC of the virgins become swollen 3 h after first mating. In tannic acid incubated tissues, more released granules were seen in CDC from snails 12 h after first mating than in CDC from virgin and castrated snails. Autoradiography showed more silver grains on the CDC from snails 12–48 h after first mating than on those from snails 3–6 h after first mating. It is suggested that, in Helisoma, mating provides a stimulus to the CDC for increased protein synthesis and release of the putative egg-laying hormone.