Molt-inhibiting hormone stimulates vitellogenesis at advanced ovarian developmental stages in the female blue crab, Callinectes sapidus 1: an ovarian stage dependent involvement

Nilli Zmora,J Sook Chung,John Trant,Yonathan Zohar

doi:10.1186/1746-1448-5-7

Nilli Zmora, J Sook Chung + Show 2 more

Open Access

https://doi.org/10.1186/1746-1448-5-7

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Abstract

To understand the hormonal coordination of the antagonism between molting and reproduction in crustaceans, the terminally anecdysial mature female Callinectes sapidus was used as a model. The regulatory roles of crustacean hyperglycemic hormone (CHH) and molt-inhibiting hormone (MIH) in vitellogenesis were examined. A competitive specific RIA was used to measure the levels of MIH and CHH in the hemolymphs of mature females at pre- and mid- vitellogenic stages, and their effects on vitellogenesis at early (early 2, E2) and mid vitellogenesis (3) stages were determined in vitro. A hepatopancreas fragments incubation system was developed and the levels of vitellogenin (VtG), as well as VtG mRNA and heterogeneous nuclear (hn)VtG RNA were determined using RIA or QPCR, respectively. MIH titers were four times higher at mid-vitellogenesis than at pre-vitellogenesis, while CHH levels in the hemolymph were constant. In the in vitro incubation experiments, MIH increased both VtG mRNA levels and secretion at ovarian stage 3. At stage E2, however, MIH resulted in a mixed response: downregulation of VtG mRNA and upregulation of hnVtG RNA. CHH had no effect on any of the parameters. Actinomycin D blocked the stimulatory effects of MIH in stage 3 animals on VtG mRNA and VtG, while cycloheximide attenuated only VtG levels, confirming the MIH stimulatory effect at this stage. MIH is a key endocrine regulator in the coordination of molting and reproduction in the mature female C. sapidus, which simultaneously inhibits molt and stimulates vitellogenesis.

Highlights

It has been proposed in decapod crustaceans that the high energy demanding processes of molting and reproduction are mutually antagonistic and do not occur simultaneously [1]
molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH) titers in the hemolymph of reproductive females Neuropeptides in the hemolymph were determined by specific radioimmunoassay (RIA) in 10 females at ovarian stages 1 and 3, representing pre-vitellogenic and midvitellogenic stages, respectively
In vitro incubation of hepatopancreas fragments The effects of sinus gland neuropeptides (CHH and MIH) on VtG expression and secretion To establish an in vitro bioassay, a preliminary experiment was conducted to determine the effect of incubation period on the stability of total RNA and VtG mRNA as well as the optimal incubation time and dose of neuropeptides for hepatopancreas fragments in vitro

Summary

Introduction

It has been proposed in decapod crustaceans that the high energy demanding processes of molting and reproduction are mutually antagonistic and do not occur simultaneously [1]. The phenomenon of reproductive phase accompanied by terminal anecdysis (halt of molting cycles) is found in only a few decapod crustaceans, including Maja squinado, Libinia emarginata, and Chionoecetes bairdi [4,5,6,7]. Most of these anecdysial animals are characterized by a degenerated molting gland, the Y-organ (YO), and the resulting low levels of molting hormones (ecdysteroids) in the hemolymph [8].

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