Effects of three vertebrate hormones on the growth, development, and reproduction of the tomato moth, Lacanobia oleracea L. (Lepidoptera: Noctuidae).

In recent years, concern has been growing that numerous manmade chemicals entering the environment are capable of mimicking endogenous hormones in wildlife. In an attempt to define and evaluate the possible impact of endocrine-disrupting substances (EDS) on insects, three vertebrate hormones were tested for their effects on growth, development, and reproduction of the tomato moth. Lacanobia oleracea. Dietary administration of estrogen or thyroxine caused a significant increase in the length of the third, fourth, fifth, and sixth larval stadia (p < 0.001). The mean time for development of the pupa, however, was not significantly different between treatments. Relative to the control groups, a significant (p < 0.05) reduction in the mean weights of fifth- and sixth-instar larvae was also observed when larvae were exposed to estrogen or thyroxine and in pupae derived from insects exposed to thyroxine or testosterone (p < 0.001). Despite this, the number of larvae that survived to adulthood was not affected by any of the treatments; neither was the pupal sex ratio affected. However, exposure of larvae to testosterone significantly (p < 0.05) increased the number of deformed pupae. In addition, the reproductive potential of adults derived from the testosterone treatment was markedly reduced. Exposure of L. oleracea larvae to this steroid caused a highly significant (p < 0.001) decrease in egg production. coupled with a significant (p < 0.05) decrease in egg viability. The physiological effects observed in L. oleracea and their possible causes are presented in this paper, and the likely impact of EDS and their effects on terrestrial invertebrates are discussed.