Endocrine control of ovarian development and flight muscle histolysis in a wing dimorphic cricket, Modicogryllus confirmatus

Abstract

The role of juvenile hormone, juvenile hormone esterase and 20-hydroxyecdysone in regulating ovarian development and flight muscle histolysis was examined in a wing dimorphic cricket, Modicogryllus confirmatus. Topical application of a juvenile hormone analog, methoprene, increased egg production and incidence of flight muscle histolysis in both intact and neck-ligated long-winged adults. Flight muscle histolysis appeared to proceed without interruption once it was initiated. Exogenous juvenile hormone III stimulated flight muscle histolysis but failed to elicit any significant effect on ovarian development. It is likely that flight muscle histolysis is an all-or-none response triggered by a pulse of juvenile hormone while ovarian development requires a continuous exposure to the hormone and shows a graded response. Injection of 20-hydroxyecdysone elicited no influence on ovarian development or flight muscle histolysis. The juvenile hormone esterase profiles provided no direct evidence to explain the morph-specific differences in egg production and the occurrence of flight muscle histolysis. However, a significant inverse relationship between juvenile hormone esterase activity and corpus allatum size may suggest that this enzyme plays a role in regulating the juvenile hormone titer in each wingmorph.