Morphogenetic effects of hydroprene on genitalia of the oriental cockroach (Dictyoptera: Blattidae)

Hydroprene had a considerable effect on the morphogenesis of external genitalia of the oriental cockroach, Blatta orientalis L. Exposure of nymphs to hydroprene resulted in abnormal adultoids with structural and positional distortions, and reduced or absent cuticular sclerotizations of the external genitalia. Late nymphal instars were significantly more sensitive to hydroprene than were early instars. In males, the epithelial cells of wings, serrata of the right phallomere, titillator and other lobes of the left phallomere were sensitive to hydroprene. The left phallomere was often prolapsed, distorted, and reduced in sclerotization. The right phallomere, particularly the serrata, was extremely malformed. In severe cases, phallomeres were entirely distorted or fused to each other. In females, the overall structure of the ovipositor appeared flaccid, less sclerotized, and misshapen. The first and second pairs of valvulae were often misshapen and reduced in sclerotization and length, or even fused with the third valvulae. This study provides morphological evidence that B. orientalis with malformed genitalia after treatment with hydroprene would be unsuccessful in copulation and fertilization. A high correlation between wrinkled wings and malformed male genitalia can be an important criterion to evaluate the effects of hydroprene on this species.