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Fish Sci (2011) 77:121DOI 10.1007/s12562-010-0301-z
REVIEW ARTICLE
Mechanisms and control of vitellogenesis in crustaceans
T. Subramoniam
Received: 13 May 2010 / Accepted: 7 October 2010 / Published online: 16 November 2010 The Japanese Society of Fisheries Science 2010
Abstract Crustaceans produce complex yolk proteins to meet the substrate and energy requirements of embryonic development. Early electron microscopic investigations point to a biphasic yolk synthesis, rst within the ovary, followed by heterosynthesis at extra-ovarian sites. Recent advances in molecular techniques have enhanced our understanding of the genetic control of yolk synthesis in crustaceans. Amino acid sequencing of crustacean vitellogenin (Vg) has enabled the elucidation of the cDNA sequence associated with it, the identication of genes, and the examination of their expression patterns in different tissues. Yolk processing in crustaeans involves cleavage of the pro-Vg at consensus sites by subtilisin-like endopro-teases within the hepatopancreas, hemolymph and oocytes. The structural elucidation of crustacean yolk proteins, as well as the comparison of amino acid sequences of vitellogenins from various crustacean species, has revealed molecular phylogenetic relationships not only among them but also with other large lipid transfer lipoproteins of disparate function. The combinatorial effects of eyestalk neuropeptides and a variety of trophic hormones achieve the hormonal coordination of molting and reproduction. Biogenic amines secreted by the central nervous system may also play an integrative role by stimulating neuro-peptide secretion.
Keywords Vitellogenesis Vitellogenin receptor
Yolk processing Neuropeptides Methyl farnesoate
Ecdysteroids 17b-Estradiol
Introduction
Many malacostracan crustaceans produce large numbers of yolk-laden eggs and brood them externally for extended periods. Hence, vitellogenesis, the process of yolk formation, is central to oogenesis. In Crustacea, vitellogenesis is a biphasic event consisting of autosynthesis and hetero-synthesis [1]. This contention is supported by recent molecular studies demonstrating yolk protein gene expression both in ovary and hepatopancreas. Receptor-mediated endocytosis of the yolk precursor molecule, vitellogenin (Vg), into growing oocytes has been established in crustaceans [2]. The molecular transformation of Vg into nal yolk products for deposition in the mature oocyte is another crucial event in vitellogenesis.
A dening feature in the endocrine regulation of vitellogenesis in Crustacea is the occurrence of inhibitory hormones in the neurosecretory cells of the X-organ/sinus gland complex within the eystalk. Conversely, many hormonal factors as diverse in nature as methyl farnesoate (MF)...