Regulation of vitellogenesis by selected endocrine modulators in crab Oziothelphusa senex senex, with special reference to methyl farnesoate

Abstract

Using vitellogenin (Vtg) gene as a biomarker, the possible role of selected endocrine modulators (EMs) such as methyl farnesoate (MF), 17α-hydroxy progesterone (17α-OHP), biochanin-A, methionine enkephaline (ME) and arachidonic acid on female reproduction in crab Oziothelphusa senex senex (O. senex senex) was elucidated in this study. The injections were given on 1st and 7th day of experiment (10−8 moles/crab) of each EMs to its respective groups and corresponding concurrent controls (CC) received solvents of EMs and sacrificed on 14th day of experiment. Found hepatopancreatic Vtg expression in MF and 17α-OHP injected crabs with significant (p < 0.05) increase in ovarian index (OI), oocyte diameter (OD) and ovarian Vtg levels and this was supported by RT-PCR results. Densitometry result of RT-PCR says that the hepatopancreatic Vtg expression is high in MF (74.51 ng) injected group than 17α-OHP (48.62 ng) injected group. Due to this, further group of females were injected with 10−8 moles/crab of MF in an alternative day along with the groups of eyestalk ablated (ESX) and CC for 28 days. Significant reduction in length of reproductive cycle (13 ± 2 days) by MF injections than ESX and CC, along with significant (p < 0.05) increase in OI, OD and ovarian Vtg levels were observed. In in vitro, the isolated hepatopancreas fragments were incubated in M199 medium with and without MF (at 10−8 moles/well) at 25 ± 1 °C in CO2 incubator. Vtg expression in hepatopancreas was found at 3rd and 6th hour of incubation in vitro and observed high density bands at 3rd h (67.21 ng) than 6th hour (56.90 ng) in RT-PCR. This is the first report stating the direct effect of MF on hepatopancreatic Vtg gene expression in crab O. senex senex. The results clearly suggest that MF and 17α-OHP have stimulatory effect on vitellogenesis and MF has direct effect on crab O. senex senex hepatopancreatic Vtg expression. Keywords: Vitellogenin expression, Vitellogenesis, Methyl farnesoate, 17α, -Hydroxy progesterone, Oziothelphusa