Ovarian protein synthesis in the prawn Macrobrachium rosenbergii: Does ovarian vitellin synthesis exist?

During the reproductive cycle oocytes of Macrobrachium rosenbergii females grow in diameter from 20 µm to 650 µm, while the gonado-somatic index increases from 0.2 to 8.0. SDS-PAGE polypeptide profiles of the cytosolic fraction from ovaries in various stages were studied. Specific vitellin bands were identified by immunoblotting. In vitro synthesis of protein was measured by TCA precipitation and autoradiography of SDS-PAGE separated polypeptides. Incorporation of [³⁵S]-methionine and cysteine was highest in animals having an oocyte diameter of 50-150 µm and lower in pre-vitellogenic ovaries (20-50 µm). The lowest synthesis was found in late-vitellogenic ovaries (300-500 µm). Most of the incorporation was found in non-vitellin polypeptide bands. These results suggest the existence of an extraovarian source of vitellogenin in M. rosenbergii.