Differences in juvenile hormone esterase activity between presumptive macropterous and brachypterous Gryllus rubens: Implications for the hormonal control of wing polymorphism

Abstract

The developmental profile of haemolymph juvenile hormone esterase activity was compared between presumptive macropterous and brachypterous morphs of the cricket, Gryllus rubens. Activities were measured during the penultimate and last stadia, two stadia where winglength development is sensitive to both exogenous juvenile hormone and crowding. Ester hydrolysis was the exclusive or nearly exclusive route of juvenile hormone degradation in the haemolymph. Individuals of a genetic stock nearly pure-breeding for long wings exhibited substantially higher enzyme activity during the last stadium compared with individuals of a stock pure-breeding for short wings. High juvenile hormone esterase activity strongly cosegregated with long wings in F 1 interstock crosses and in F 2 backcrosses. Crickets of the macropterous stock whose winglength development was redirected to short wings by crowding exhibited low juvenile hormone esterase activity during the last stadium, similar to individuals of the brachypterous stock. Rates of juvenile hormone hydrolysis (epoxide hydrase plus esterase activity) were also higher in wingbud homogenates from last-stadium macropterous versus brachypterous females. In contrast, haemolymph enzyme activity was similar in presumptive macropterous and brachypterous morphs during the penultimate stadium. Results suggest that variation in haemolymph juvenile hormone esterase activity during the last stadium may play an important role in wingmorph determination in Gryllus rubens.