Induction of vitellogenin and growth of implanted oocytes in male cockroaches

Vitellogenins are yolk protein precursors that are synthesised in the liver of lower vertebrates in response to ovarian hormones, and in the fat body tissue of insects, under the influence, in most species, of juvenile hormone (JH) from the corpora allata (CA). Vitellogenins are normally restricted to females, although in male amphibians and roosters their synthesis can be induced artificially by the injection of oestrogens. Thus female specificity is maintained by hormonal differences between adult males and females. In insects, on the other hand, because the CA of adults of both sexes are active, it appeared that male fat body could not normally respond to JH by synthesising vitellogenin. However, precise JH synthetic rates of male CA are only known in Schistocerca gregaria and Diplopterapunctata, in which species they are low compared to the rates in the female glands. The absence of vitellogenin in adult males could thus be due to inadequate JH titres. We report here that synthesis of vitellogenin can indeed be induced in males of Diploptera by implantation of female CA or application of Diploptera by implantation of female CA or application of a JH analogue, ZR512 (Zoecon), and that implanted oocytes take up the vitellogenin.