Termination of Pregnancy and Milk Synthesis in the Viviparous Cockroach,Diploptera Punctata: a Role of Juvenile Hormone

Summary Females of the viviparous cockroach Diploptera punctata nourish their embryos with a milk secretion produced by the brood sac wall. Milk content of the brood sac undergoes a decline a few days prior to parturition. We have shown that this decline is dependent on juvenile hormone produced by the corpora allata. Allatectomy either early or late in pregnancy, times when juvenile hormone titer is low, delayed the normal decline of milk in the brood sac. Treatment of allatectomized females with the juvenile hormone analogue, ZR 512, restored the normal decline in the amount of milk. Fine structural analysis as well as injection of radiolabeled precursor demonstrated that the amount of milk in the brood sac at the end of gestation in allatectomized females reflected continued milk synthesis and not merely stasis. Corpora allata were shown to have the additional role of terminating pregnancy. Allatectomy of pregnant females delayed parturition even though it did not affect embryo development. Replacement therapy with juvenile hormone analogue restored normal parturition time.