Isolation and characterization of an additional crustacean hyperglycemic hormone from the greasyback shrimp <Emphasis Type="Italic">Metapenaeus ensis</Emphasis>

Crustacean hyperglycemic hormone (CHH) is released from the X-organ/sinus gland complex located in the eyestalks. In this study, the most abundant CHH in the sinus gland of the greasyback shrimp Metapenaeus ensis was purified by reversed-phase HPLC and identified by N-terminal amino acid sequencing. Although two CHH molecules (Mee-CHH-A and Mee-CHH-B) have already been identified from M. ensis by cDNA cloning, this study revealed the presence of an additional CHH peptide based on differences in the N-terminal amino acid sequences of the CHH-A and CHH-B. Therefore, this novel CHH was designated as Mee-CHH-C. A cDNA encoding the Mee-CHH-C precursor was cloned by RT-PCR coupled with 5′- and 3′-RACE, and it was found that the mature Mee-CHH-C consisted of 72 amino acid residues containing 6 conserved cysteine residues and possessed an amidated C terminus. Mee-CHH-C had 62 and 68% identities with Mee-CHH-A and Mee-CHH-B, respectively, and was highly homologous to CHHs characterized from other penaeid shrimp species. The hyperglycemic activity of Mee-CHH-C was examined by an in vivo bioassay using the kuruma prawn Marsupenaeus japonicus. Injection of Mee-CHH-C increased hemolymph glucose levels significantly and dose-dependently. These results indicate that Mee-CHH-C is possibly one of the major molecules in M. ensis that regulate glucose levels in the hemolymph.     

Annual reproductive cycle of the greasyback shrimp Metapenaeus ensis in Ise Bay,Japan

The greasyback shrimp Metapenaeus ensis is widely distributed along the coast of India and the West Pacific where it is an important fisheries species. We have examined seasonal changes in ovarian development, spermatogenesis, and mating of Me. ensis in histological studies and by external observations on specimens collected in Ise Bay, its northernmost habitat. Ovaries were found to be previtellogenic from February to May, with the first signs of development being the accumulation of yolk in oocytes in late May. Ovarian shadow ratios were high during the period late July to mid-September. The formation of cortical rods in the peripheries of oocytes and germinal vesicle breakdown were observed in ovaries from late June to September. Male shrimps had sperm in the testes during the period early June to early October, and female shrimps had spermatophores in spermatheca after early July. In late July, some post-spawn female shrimps had exogenous vitellogenic oocytes in their ovaries, indicating that ovarian development had been repeated in preparation for the next spawning. Ovarian shadow ratios, which were positively correlated with gonadosomatic indices and ovarian development, seem to be a useful marker to determine ovarian development. Our results indicate that mating in Me. ensis started in early July and that the spawning season ranged from July to September with more than two cycles of spawning in Ise Bay.