The effect of heat stress (38 °C) on the content of octopamine (OA) and 20-hydroxyecdysone (20HE) was studied under normal and stressful conditions in adult flies of Drosophila virilis lines contrasting in the level of the juvenile hormone (JH). The wild-type flies (line 101) exhibited a pronounced sex dimorphism for the content of both OA and 20HE, which was substantially lower in this line than in flies of the mutant line 147. The level of both hormones increased in flies of line 101 exposed to heat stress, whereas it remained unchanged in flies of line 147 under the same conditions. The effect of heat stress on the level of JH metabolism and fertility was also studied in D. melanogaster wild-type lines and lines carrying mutations in genes responsible for OA and DA syntheses. In octopamineless females of the TβhnM18 line and in females of the Ste line characterized by a doubled content of DA, JH degradation differed from normal: it was increased in both young and mature TβhnM18 females, while decreased in young and increased in mature Ste flies. Fertility was substantially lower in the Ste than in the wild-type line. Flies of all of the D. melanogaster lines produced a stress response; however, in mutant lines, both fertility and stress reactivity of the systems controlling JH metabolism differed significantly from that of the wild-type lines. The role of JH, 20HE, OA, and DA interaction in regulation of Drosophila reproduction under stressful conditions is discussed.
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