ABSTRACT
The present study investigated the effect of arachidonic acid (AA) and selected prostaglandins on the regulation of vitellogenesis, ecdysteroidogenesis and methyl farnesoate (MF) synthesis in the freshwater crab Oziotelphusa senex senex and the giant mud crab, Scylla serrata Administration of AA and prostaglandin F2α (PGF2α) and prostaglandin E2 (PGE2) significantly increased ovarian index, oocyte diameter and ovarian vitellogenin levels and ecdysteroid and MF levels in the hemolymph of crabs. Secretions of MF and ecdysteroids from in vitro cultured mandibular organs (MO) and Y-organs (YO) isolated from intermolt crabs injected with AA, PGF2α and PGE2 were greater when compared with controls. In contrast, injection of prostaglandin D2 (PGD2) had no effect on vitellogenesis, ecdysteroid and MF levels in circulation. In vitro secretion of MF from MO explants isolated from avitellogenic crabs incubated with AA, PGF2α and PGE2 increased in a time-dependent manner. Conversely, incubation of YOs isolated from avitellogenic crabs with AA, PGF2α and PGE2 had no effect on secretion of ecdsyteroids. These results implicate prostaglandins in the regulation of reproduction by inducing the synthesis of MF and consequent ecdysteroid synthesis in brachyuran crabs, and provide an alternative molecular intervention mechanism to the traditional eyestalk ablation methodology to induce vitellogenesis and ovarian maturation in crustaceans.
Subject(s)
Arachidonic Acid/administration & dosage , Brachyura/physiology , Ecdysteroids/metabolism , Fatty Acids, Unsaturated/metabolism , Prostaglandins/administration & dosage , Vitellogenesis/physiology , Animals , Brachyura/drug effects , Female , Species Specificity , Vitellogenesis/drug effectsABSTRACT
The possible involvement of 13-cis retinoic acid (CRA) in the regulation of ovarian development in Oziotelphusa senex senex was investigated. Injection of CRA, into avitellogenic crabs significantly increased ovarian index, oocyte diameter and ovarian vitellogenin levels. Injection of CRA also resulted in a significant increase in the secretory rates of mandibular organs and Y-organs and circulatory levels of the methyl farnesoate and ecdysteroids. Further, administration of CRA into avitellogenic crabs produced higher amounts of Retinoid X Receptor, Ecdysteroid Receptor, E75 and vitellogenin mRNAs in the hepatopancreas. Mandibular organ and Y-organ explants isolated from avitellogenic crabs secreted more of methyl farnesoate and ecdysteroids respectively when incubated with CRA. Taken together, these observations led us to hypothesize that CRA stimulates ecdysteroidogenesis and methyl farnesoate synthesis, up-regulates EcR, RXR and E75 expression in hepatopancreas, which then induces vitellogenin gene expression. Vitellogenin is subsequently taken up from hemolymph by ovaries ensuing in ovarian maturation.
Subject(s)
Brachyura/physiology , Isotretinoin/metabolism , Vitellogenesis/physiology , Animals , Brachyura/growth & development , Ecdysteroids/metabolism , Egg Proteins/genetics , Enzyme-Linked Immunosorbent Assay , Female , Fresh Water , Hemolymph/metabolism , Hepatopancreas/metabolism , Ovary/growth & development , RNA, Messenger/metabolism , Receptors, Cell Surface/genetics , Receptors, Steroid/genetics , Retinoid X Receptors/genetics , Retinoid X Receptors/metabolismABSTRACT
In the current study, we have examined the role of serotonin in regulating the levels of methyl farnesoate and ecdysteroids in the giant mud crab Scylla serrata and validated that serotonin indeed is a reproductive hormone. Administration of serotonin elevated circulatory levels of methyl farnesoate and ecdysteroids in crabs. Since methyl farnesoate and ecdysteroid act through retinoid X receptor (RXR) and ecdysteroid receptor (EcR) respectively and these receptors are involved in the regulation of reproduction in crustaceans, we have determined the mRNA levels of RXR and EcR in hepatopancreas and ovary after serotonin administration. The expression levels of both RXR and EcR increased significantly in the hepatopancreas and ovary of serotonin injected crabs when compared to the controls. In vitro organ culture studies revealed that incubation of Y-orgas and mandibular organ explants in the presence of serotonin resulted in a significant increase in the secretion of ecdysteroids by Y-organs, but without alterations in MF synthesis in mandibular organs. From the above studies it is evident that serotonin stimulates Y organs resulting in increased ecdysteroidogenesis. Though the circulatory levels methyl farnesoate elevated after serotonin administration, organ culture studies revealed serotonin mediated methyl farnesaote synthesis is indirect probably by inhibiting release of mandibular organ inhibiting hormone from eyestalks.
Subject(s)
Arthropod Proteins/genetics , Brachyura/drug effects , Ecdysteroids/biosynthesis , Fatty Acids, Unsaturated/biosynthesis , Receptors, Steroid/genetics , Serotonin/pharmacology , Amino Acid Sequence , Animals , Arthropod Proteins/metabolism , Base Sequence , Brachyura/genetics , Brachyura/growth & development , Ecdysteroids/agonists , Eye/drug effects , Eye/growth & development , Eye/metabolism , Fatty Acids, Unsaturated/agonists , Female , Gene Expression Regulation , Hepatopancreas/drug effects , Hepatopancreas/growth & development , Hepatopancreas/metabolism , Mandible/drug effects , Mandible/growth & development , Mandible/metabolism , Organ Culture Techniques , Ovary/drug effects , Ovary/growth & development , Ovary/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, Steroid/metabolism , Reproduction/drug effects , Reproduction/genetics , Retinoid X Receptors/genetics , Retinoid X Receptors/metabolism , Serotonin/metabolism , Signal TransductionABSTRACT
The objective of the present study was to investigate the expression profile of retinoid X receptor (RXR), ecdysone receptor (EcR) and ecdysone inducible gene (E75) in the hepatopancreas and ovary of Oziothelphusa senex senex during different vitellogenic stages. RXR, EcR and E75 complementary DNAs (cDNAs) were isolated from the ovaries, while vitellogenin (VtG) cDNA was isolated from the hepatopancreas of vitellogenic female crab. Deduced amino acid sequence of the messenger RNAs (mRNAs) of RXR, EcR and E75 showed more than 80% identity with their respective mRNAs of other brachyurans. VtG mRNA was not detected in the ovary throughout vitellogenic stages. RXR and EcR were significantly increased in the ovaries during vitellogenic stage I. The levels of EcR, E75 and VtG in the hepatopancreas elevated significantly during vitellogenic stages I and II, whereas the levels of RXR elevated only in vitellogenic stage I. During vitellogenic stage III, the levels of RXR, EcR and VtG in the hepatopancreas were significantly decreased. Immunoprecipitation analysis revealed the presence of VtG in the haemolymph, hepatopancreas and ovary extracts from the females but absent in haemolymph and hepatopancreas extract of males. It can be inferred that RXR, EcR and E75 are involved in the regulation of synthesis of VtG in hepatopancreas, whereas in ovary, it is hypothesized that they play an important role in the uptake of VtG from the haemolymph, probably by regulating the levels of vitellogenin receptor. These are the first data showing an association between the expression levels of RXR, EcR and E75 and vitellogenesis and provide an alternative molecular intervention mechanism to the traditional eyestalk ablation to induce vitellogenesis and ovarian maturation in crustaceans.
