EVOLUTIONARY ENDOCRINOLOGY OF JUVENILE-HORMONE ESTERASE IN GRYLLUS-ASSIMILIS - DIRECT AND CORRELATED RESPONSES TO SELECTION

Hemolymph juvenile hormone esterase (JHE) activity on the third day of the last stadium in the cricket, Gryllus assimilis, exhibited a signi ficant response to selection in each of six replicate lines. Mean real ized heritability was 0.26 +/- 0.04. The response was due to changes i n whole-organism enzyme activity as well as to changes in the proporti on of enzyme allocated to the hemolymph compartment. In vivo juvenile hormone metabolism differed between some lines selected for high vs. l ow enzyme activity. Only minimal differences were observed between lin es with respect to hemolymph protein concentration or whole-cricket ac tivity of juvenile hormone epoxide hydrolase, the other major JH-degra ding enzyme. Dramatic correlated responses to selection, equal in magn itude to the direct response, were observed for JHE activity on each o f three other days of the last juvenile stadium. In contrast, no corre lated responses in JHE activity were observed in adults. This indicate s that JHE activities throughout the last stadium will evolve as a hig hly correlated unit independent of adult activities and the evolution of endocrine mechanisms regulating juvenile development can be decoupl ed from those controlling adult reproduction. This study represents th e first quantitative-genetic analysis of naturally occurring endocrine variation in an insect species.