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 e ntering the environment are capable of mimicking endogenous hormones in wil dlife. In an attempt to define and evaluate the possible impact of endocrin e-disrupting substances (EDS) on insects, three vertebrate hormones were te sted for their effects on growth, development, and reproduction of the toma to moth, Lacanobia olerancea. Dietary administration of estrogen or thyroxi ne 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 weig hts of fifth- and sixth-instar larvae was also observed when larvae were ex posed 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; neith er was the pupal sex ratio affected. However, exposure of larvae to testost erone significantly (p < 0.05) increased the number of deformed pupae. In a ddition, the reproductive potential of adults derived from the testosterone treatment was markedly reduced. Exposure of L. oleracea larvae to this ste roid caused a highly significant (p < 0.001) decrease in egg production, co upled with a significant (p < 0.05) decrease in egg viability. The physiolo gical effects observed in L. oleracea and their possible causes are present ed in this paper, and the likely impact of EDS and their effects on terrest rial invertebrates are discussed.