Meeting Abstract
Reproduction in female crustaceans is controlled via the coordination of various hormones. In this study, the effects of a red-pigment concentrating hormone (Liv-RPCH) previously cloned from eyestalks, on ovarian growth were assessed. Artificially-synthesized Liv-RPCH was employed in both in vitro and in vivo assays; various measurements were conducted in order to evaluate the influence of Liv-RPCH on different physiological parameters. In a 24-hr in vitro incubation, RPCH alone did not stimulate oocyte growth; only ovaries co-incubated with either brain or thoracic ganglia with the addition of Liv-RPCH showed a significant increase in mean oocyte area. Regarding in vivo experimentation, measurements including that for ovarian Vg mRNA levels, hemolymph vitellogenin concentrations, and mean oocyte area were performed 25 days after the injection of Liv-RPCH. Results showed that Vg mRNA expression in ovaries, circulatory vitellogenin concentrations, as well as mean oocyte area were all significantly increased in animals receiving Liv-RPCH. Evidence from other lines had suggested that serotonin (5-HT) may stimulate ovarian growth in crustaceans. To further elucidate whether Liv-RPCH is involved in 5-HT induced-ovarian maturation, Liv-RPCH expression was examined in eyestalks, brain, thoracic ganglia and ovaries by means of quantitative real-time PCR at 0, 3 and 6 hr after 5-HT injection. The mRNA levels of Liv-RPCH in eyestalks, brain, and thoracic ganglia showed no significant changes within 6 hr after injection. However, the expression of Liv-RPCH in the ovaries was upregulated after 3 and 6 hr of 5-HT injection, suggesting that Liv-RPCH is involved directly or indirectly in 5-HT-stimulated ovarian growth. Overall, the above results strongly suggest that Liv-RPCH participates in ovarian growth in L. vannamei .
