Ovulation hormone, nutritive state, and female reproductive activity in Lymnaea stagnalis.

A study of the relation between nutritive state and female reproductive activity as affected by the ovulation hormone (CDCH) has been made in the freshwater pulmonate snail Lymnaea stagnalis. CDCH is produced by the neuroendocrine caudodorsal cells (CDC) in the cerebral ganglia. Spontaneous oviposition ceased within 6 days of the beginning of a starvation period. This is most probably partially due to a reduction in the CDC activities because (1) quantitative electron microscopy showed a nearly 80% decrease in the number of release phenomena in the CDC-axon terminals in the neurohemal area in the intercerebral commissure, and (2) a bioassay showed a considerable reduction in the amount of CDCH in this area. During starvation the ovotestis and the female accessory sex organs became progressively less sensitive and, after 25 days, were completely insensitive to injected CDCH. This was indicated by a decrease in the responses to CDCH injection and, correspondingly, by a gradual increase in the CDCH thresholds for ovulation and egg formation. It is argued that the insensitivity may be caused by a reduction in the activities of the endocrine dorsal bodies. During refeeding, CDCH injections again become effective in inducing egg mass production, followed by resumption of spontaneous oviposition. This suggests a rapid restoration of DB and CDC activities following refeeding.