The effect of ovary implants on juvenile hormone production by corpora allata of male Diploptera punctata

In the cockroach Diploptera punctata, vitellogenic basal oocytes stimulate juvenile hormone production by the corpora allata. Experiments with males were designed to determine whether oocytes must grow vitellogenically in order to stimulate juvenile hormone production. Two ovarioles with vitellogenic basal oocytes were implanted into unoperated and sham-operated males that do not produce vitellogenin, and males with denervated corpora allata, that produce more juvenile hormone, and sometimes more vitellogenin. Males with corpora allata in similar conditions were injected with saline as controls. In males with denervated corpora allata compared to sham-operated and unoperated males, the implanted basal oocytes showed a greater increase in length, protein, and vitellin content. Juvenile hormone synthesis by denervated corpora allata in males with ovariole implants was greater than in controls. In 10 of 50 males with denervated corpora allata in which one or no ovarioles grew, juvenile hormone production was not higher than in controls. This suggests that if sufficient juvenile hormone is not present to produce vitellogenin, or oocytes do not take vitellogenin up, juvenile hormone production is not stimulated. In sham-operated males implanted with ovarioles, no difference was detected in juvenile hormone synthesis compared to controls. However, when unoperated males were used, a significant increase was detected. This suggests that intact nerves from the brain to the corpora allata restrained juvenile hormone production so that ovarioles could elicit only slight stimulation of the corpora allata, and oocytes continued vitellogenesis but more slowly than in denervated males. Thus the extent of vitellogenesis appears to determine the ability of ovaries to stimulate juvenile hormone production.