A NEUROPEPTIDE FAMILY FROM THE SINUS GLAND OF THE MEXICAN CRAYFISH, PROCAMBARUS-BOUVIERI (ORTMANN)

The main neuroendocrine axis of crustaceans is constituted by the brai n, medulla terminalis X-organ (MTXO)-sinus gland (SG) system. A variet y of hormonal peptides are synthesized in the MTXO where the peptiderg ic neuronal somata are situated. The peptides are then transported via axenic how to the SG, which is a conglomerate of bulbous axenic termi nals in close contact with the hemolymph, where these hormones are lib erated to the circulation by a process of exocytosis. Four peptides ha ve been isolated from crude aqueous extracts of microdissected SC of t he Mexican crayfish, Procambarus bouvieri, by means of a single-step r everse-phase high pressure liquid chromatography (RP-HPLC) on a mu Bon dapak-Phenyl column; these have been characterized physiologically by specific bioassays, and structurally by means of tryptic peptide mappi ng and sequencing. These procedures have identified (in the order of e lution) a gonad-inhibiting hormone (GIH), a molt-inhibiting hormone (M IH), a major isomorph of the crustacean hyperglycaemic hormone (CHH-I) and its minor isomorph (CHH-II), in approximate concentrations of 5, 18, 60, and 20 ng per SG, respectively. Their common characteristics a re: (1) acidic pl, (2) hydrophobicity, (3) molecular masses between 83 00 and 8400 Da, (4) approximately 72 amino acid residues, (5) blocked N- and C-termini, (6) six cysteines forming three disulfide bridges, ( 7) lack of histidine, methionine, and tryptophan residues, (8) long tr acts of sequence identity. These features clearly establish these four peptides as members of one neuropeptide family. Recently, a factor wi th gonad-stimulating activity has been isolated from this same crude e xtract by means of RP-HPLC. This factor stimulated by 300% the specifi c incorporation of radioactive leucine into yolk proteins in an in vit ro bioassay consisting in the incubation of ovary fragments from the a dult female shrimp, Penaeus vannamei, and immunoprecipitation of the p roteins with a specific antibody to shrimp yolk protein. Thus, the SG extract from the crayfish, P. bouvieri, contains both a gonad-inhibiti ng hormone and a gonad-stimulating hormone (GSH), capable of acting on ovarian yolk protein synthesis in the shrimp, P. vannamei. The output of shrimp larvae spells the success of a shrimp hatchery. The inducti on of maturation of shrimp in captivity is done at present via eyestal k ablation of female broodstock, but this method causes increased mort ality, disruption of the shrimp's endocrine system, and decreased larv al viability with repeated spawnings. GSH could be used in aquaculture to increase the effect of eyestalk ablation or to substitute for this procedure completely.