How do hormones regulate reproduction in molluscs and echinoderms
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Among molluscs the optic glands of the cephalopods and the dorsal bodies of the gastropods are endocrine organs which are involved in the regulation of reproductive processes. The optic glands stimulate the differentiation of the sex cells, spermatogenesis and vitellogenesis, and the growth of the female tract. The male tract is controlled by these glands via the testis. The dorsal bodies stimulate vitellogenesis, and the growth and differentiation of the reproductive tract. In hermaphrodite gastropods the differentiation of male sex cells is dependent on the presence of a factor produced by the cerebral ganglia, whereas the female cells show autodifferentiation. Data on the role of neurosecretory cells in the reproduction of molluscs are scarce. The neurosecretory bag cells of the abdominal ganglion in Aplysia are known to stimulate ovulation. There are some indications that the optic tentacles play a part in regulating reproduction, but the mechanism is, as yet, not clear.