Meeting Abstract

81.5  Tuesday, Jan. 6  An additional role for molt-inhibiting hormone in the mature female blue crab Callinectes sapidus as a vitellogenesis stimulating hormone ZMORA, N.*; TSUTSUI, N.; TRANT, J.; CHUNG, J. Sook; University of Maryland Biotechnology Institute, Baltimore chung@comb.umbi.umd.edu

Molting and reproduction in crustaceans are hormonally controlled by the family of crustacean hyperglycemic hormone (CHH) neuropeptides. To test the role of these neuropeptides of CHH and molt-inhibiting hormone (MIH) in the control of vitellogenesis in the female Callinectes sapidus, we profiled the expression levels of these genes and hemolymph titers during the reproductive cycle and their direct effect on vitellogenesis in vitro. The concentrations of MIH in hemolymph were higher at ovarian stages 2 and 3 than those at stage 1, while CHH remained constant. The data indicates that despite the females at terminally anecdysis, MIH is being expressed and secreted in a vitellogenic stage dependent manner. Tested in-vitro, MIH caused a 60% decrease in vitellogenin (VtG) mRNA, but stimulated the secretion of VtG by two folds as well as the transcription of heterogeneous nuclear VtG RNA (HnVtG) by 2.5 folds. Our results demonstrate that MIH has a stimulatory role in vitellogenesis in the female C. sapidus at the levels of transcription and translation of VtG in hepatopancreas. Furthermore, to ensure the hepatopancreas as being a target tissue of MIH, a preliminary binding study was carried out using the membranes of hepatopancreas of the vitellogenic females and [125I] MIH, together with Y organs as a reference tissue. Both tissues exhibited the specific binding sites, but with the differences in the values of KD and BMAX. Overall our data suggests that the functions of MIH in the regulation of molt and vitellogenesis are mediated through tissue specific receptors with different kinetics and signal transduction.