The effects of exogenous juvenile hormone treatment on embryogenesis in Schistocerca gregaria

Abstract

Exogenous juvenile hormone (JH) application to Schistocerca gregaria eggs interfered with normal embryogenesis in a dose- and age-dependent manner. Embryos treated between 3 to 9 days postoviposition were inhibited at (1) blastokinesis; (2) postblastokinesis; (3) as vermiform larvae; or (4) as first-instar hoppers unable to shed their provisional entitle completely. The development of 3- to 5-day-old embryos was inhibited at blastokinesis when the embryos were treated with 1 μg JH but not with 0.1 μg JH. However, sensitivity increased with age, so that 8-to 9-day-old embryos were unable to shed the provisional cuticle when treated with as low as 0.01 μg JH. Treatment of embryos later than 10 days after oviposition did not disrupt embryogenesis and did not result in postembryonic aberrations at any stage in the life cycle. Furthermore, exogenous JH treatment of developing embryos did not enhance solitarization of S. gregaria.Disruption of embryogenesis was accompanied by an increase in brown coloration of the embryos. Microscopic examination revealed an interference with the normal development of the provisional cuticle.