Prolonged negative selection of Drosophila melanogaster for a character ofadaptive significance disturbs stress reactivity

The metabolism of juvenile hormone by JH-esterase and JH-epoxide hydrolase, and octopamine by tyrosine decarboxylase were studied under normal and str ess conditions in flies of two related lines of D. melanogaster. One was se lected for high (HA line) and another for low (LA line) male sexual activit y for more than 700 generations. It was demonstrated that prolonged selecti on for low male sexual activity results in considerable changes in both sys tems. Tyrosine decarboxylase activity in males and females of the LA line w as sharply reduced as compared with those of the HA and controle Canton-S l ines; JH-esterase and JH-epoxide hydrolase activities were decreased in fem ales, and not in males, of the LA line. It was demonstrated that the respon se of both metabolic systems to heat stress is impaired in individuals of t he LA line: the system of juvenile hormone metabolism does not respond to s tress, and that of octopamine metabolism is decelerated. The role of juveni le hormone metabolism in male reproductive function is discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.