Molluscus - Hormones in Growth and Reproduction
We know quite well about the endocrine mechanism of growth and reproduction in the freshwater snail Lymnaea stagnalis. This is a gastropod, and such as other gastropods, Lymnea is protandric hermaphrodite. That means, in these groups of animals, male gonads mature first and this is followed through the maturation of the female gonad. The dorsal bodies produce hormones that promote development of both male and female phases of reproductive organs. In the female phase these glands generate pronounced effects. They stimulate maturation, yolk deposition in the eggs, ovulation and oviposition. They as well stimulate growth and differentiation of the female accessory sex organs. In this animal, specific groups of neurosecretory cells of the cerebral ganglia produce a hormone (growth hormone) that stimulates growth and differentiation of the female accessory sex organs. In this animal, specific groups of neurosecretory cells of the cerebral ganglia produce a hormone (growth hormone) which stimulates growth of the body. Conversely the lateral lobes attached to the brain produce a growth-retarding hormone. This hormone not only retards growth of the body but as well causes an increase in egg production. The optic glands of the cephalopod mollusc Octopus control reproduction in the male and female. The glands secrete a gonadotropic hormone at the onset of sexual maturity. This stimulates development of the genital ducts and maturation of germ cells.