Crustacean ecdysteriods in reproduction and embryogenesis.

Ecdysteroids are the molting hormones in Crustacea, as in other arthropods. They also subserve functions in the control of reproduction and embryogenesis. The available evidence indicate that the ecdysteroids are sequestered into the ovary by binding to yolk precursor proteins. Steroidogenic ability of the ovary is yet to be demonstrated in Crustacea. Despite several investigations, the role of ecdysteroids in oocyte maturation is not fully known. However, the embryonic ecdysteroids undergo significant fluctuation, correlated to specific developmental stages, including the secretion of embryonic envelopes and cuticle. Ecdysteroid metabolism in the eggs seems to be active throughout embryogenesis inasmuch as the free ecdysteroids are rapidly converted into conjugates, and vice versa; in addition to their inactivation into excretory ecdysteroidic acids. Eyestalk neuropeptides such as molt inhibiting hormones have a dominant role on the ecdysteroid synthesis by Y-organ, although recent evidence suggests a stimulatory role for yet another endocrine gland, the mandibular organ on Y-organ synthesis.