Perspectives on hormonal manipulation of shrimp [Macrobrachium] reproduction

Shrimp aquaculture in the world has developed remarkably, however, to enable further development, new technological advances in hormonal manipulation of shrimp reproduction are increasingly important for effective stock enhancement. To develop hormonal manipulation techniques, progress in shrimp endocrinology is necessary. In this article, I review my work and related studies on shrimp endocrinology. For female reproduction, eyestalk hormones, ecdysteroids, and vertebrate-type steroid hormones were examined. Eyestalk ablation induced ovarian development, indicating the occurrence of the eyestalk hormone, vitellogenesis-inhibiting hormone. Hemolymph levels of ecdysteroids and vertebrate-type steroid hormones were not correlated to ovarian development, suggesting that these hormones are not involved in the regulation of ovarian development. For male reproduction, the androgenic gland showed distinct structural changes in relation to male reproductive activity, suggesting that the hormone has a role in the regulation of male reproductive activity. For control of shrimp reproduction, at present, no hormones are available, and only eyestalk ablation is practically used. This is mainly because endocrinology of shrimp reproduction is not yet sufficiently understood. Only a few hormones have been detailed so far, and many hormones are still unidentified. For new technological advancements in hormonal manipulation, it is necessary to characterize these unknown hormones and to synthesize useful ones for administration.