Induction of vitellogenesis, MF synthesis and ecdysteroidogenesis in two edible crabs by arachidonic acid and prostaglandins

The present study investigated the effect of arachidonic acid (AA) and selected prostaglandins on the regulation of vitellogenesis, ecdysteroidogenesis and methyl farnesoate synthesis in the fresh water 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 methyl farnesoate levels in the hemolymph of crabs. Secretions of methyl farnesoate (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, 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 studies implicate prostaglandins in the regulation of reproduction by inducing the synthesis of methyl farnesoate 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.