The control of ovulation in the hermaphroditic freshwater snail Lymnaea stagnalis by the neurohormone of the caudodorsal cells

Abstract

Cauterization of the neurosecretory caudodorsal cells (CDC) of the cerebral ganglia of the hermaphroditic freshwater pulmonate Lymnaea stagnalis, resulted in a cessation of oviposition. Subsequent injection of homogenates of the cerebral commissures (COM) (l.5 COM/animal), the neurohaemal storage and release site of the secretion product of the CDC, induced egg-laying in all CDC cauterized snails. The mean number of eggs per egg mass produced was similar to that of untreated animals. The mean time lapse between injection and response was about 130 min. A homogenate of other nervous tissue (n. frontolabialis superior) was not capable of inducing oviposition. CDC removal from juveniles, in which vitellogenesis had hardly begun, had no effect on the formation and maturation of oocytes. However, many mature oocytes had degenerated. On the basis of these results it is concluded that the CDC produce a hormone, which controls ovulation. Injection of COM into intact, unoperated, adult snails induced egg-laying in most but not all recipients. This indicates that other factors, at present unknown, can impede the effect of the ovulation hormone.