Synchronous maturation of the female reproductive system and of the ovulation hormone-producing system in Lymnaea stagnalis.

The intercerebral commissures (COMs) of young snails, which are in the male stage (10-15 mm shell height), contain only small quantities of ovulation hormone (CDCH): 0.6 OIU . COM-1 . g-1 snail (1 ovulation inducing unit = threshold dose for ovulation in adult recipients). During the subsequent period of female maturation the quantities of CDCH increase considerably up to a maximum of 47 OIU . COM-1 . g-1 snail at the onset of oviposition. In snails smaller than ca. 21 mm shell height oviposition cannot be induced by COM extract injections. It is concluded that maturation of the female reproductive system and of the ovulation hormone system occur simultaneously, and that both processes are stimulated by the hormone of the dorsal bodies (endocrine organs located upon the cerebral ganglia).