DIRECT AND CORRELATED RESPONSES TO SELECTION ON JHE ACTIVITY IN ADULTAND JUVENILE GRYLLUS-ASSIMILIS - IMPLICATIONS FOR STAGE-SPECIFIC EVOLUTION OF INSECT ENDOCRINE TRAITS

Two-way selection on the activity of the endocrine regulator, juvenile hormone esterase (JHE), in adults of the cricket, Gryllus assimilis, resulted in a realized JHE heritability of 0.059 +/- 0.001. This herit ability was significantly lower than the realized JHE heritability mea sured previously during selection on the last juvenile stadium (0.26 /- 0.04). We observed strong correlated responses to selection on JHE activity during different periods of adulthood but very weak correlate d responses in the last juvenile stadium. The additive genetic correla tion between JHE activities in adults and juveniles, measured from the two pairs of correlated and direct responses obtained from the presen t adult and the previous juvenile selection studies, did not differ si gnificantly from zero. Lines from the earlier juvenile selection study , reassayed for correlated responses after an additional five generati ons of selection, exhibited only weak correlated responses for JHE act ivity in adult and penultimate stages. Results from the present adult and the previous juvenile selection studies provide a consistent pictu re of strong within-stage JHE correlated responses in either adult or juvenile stages. By contrast, only weak JHE correlated responses occur in contiguous developmental stages, irrespective of whether the stage s are physiologically or morphologically similar or dissimilar, or whe ther JHE activity was selected before or after the stage in which the correlated responses were measured. The regulation of a particular lif e cycle stage by JHE (juvenile development) can be modified by selecti on without necessarily altering its regulatory role in other stages (a dult reproduction).