Detection of vitellogenin in the haemolymph of larval female locusts (Locusta migratoria) treated with the neurohormone, Lom OMP

Abstract

The ovary maturating parsin of Locusta migratoria (Lom OMP) is a gonadotropic neurohormone which is active during vitellogenesis over the same period as juvenile hormone (JH). For this reason, a possible vitellogenic effect of the Lom OMP was tested using fifth instar larvae. At this last larval stadium, locusts do not normally produce vitellogenin but the synthesis of vitellogenin can be induced at this time by high doses of JH analogues. Since vitellogenin is rapidly released into the haemolymph, the synthesis of vitellogenin was investigated by detecting the occurrence of vitellogenin in the haemolymph, using SDS-PAGE. The neurohormone Lom OMP was able to induce vitellogenin synthesis in females but not in males. The maximally efficient dose-range was narrow. The timing of vitellogenin occurrence was delayed as compared to that obtained with JH. The Lom OMP inducibility, evaluated by the number of responsive females, was lower than that obtained with JH provided by the implantation of a single corpus allatum. In allatectomized females, the Lom OMP inducibility was not suppressed but, on the contrary, increased. The gonadotropic activity of the Lom OMP thus acts through a vitellogenic effect similar to the gonadotropic activity of JH but the mode of action of Lom OMP is different to and independent of that of JH.