NEUROENDOCRINE CONTROL OF ECDYSTEROID TITERS AND GONADOTROPIC CYCLES IN THE INSECT LABIDURA-RIPARIA FEMALES

Neuroendocrine controls of vitellogenesis, gonadotrophic cycles and ec dysteroid levels were examined in Labidura riparia using microsurgical manipulations, hormonal treatments, enzyme immunoassay (EIA) and high performance liquid chromatography (HPLC). In normal females high leve ls of ecdysteroids occur both in ovaries and hemolymph at the end of e ach vitellogenic cycle. In allatectomized (CA-) and pars intercerebral is cauterized females (PI-) vitellogenesis is suppressed, and ovarian ecdysteroids are at a low level. Juvenile hormone (JH) treatments rest ore vitellogenesis and high ecdysteroid levels in both experimental ca ses. Pars lateralis cauterized females (PL-) display a continuous vite llogenesis; however, ecdysteroid levels are lower in ovaries and highe r in hemolymph than in normal females. HPLC/EIA analysis of ovarian ec dysteroids was performed, and the effects of different hormonal treatm ents are described. Discussing the interactions between JH, ecdysteroi ds, gonadotrophic activity and neurosecretory centers, we point out th e role of the pars lateralis in the regulation of ecdysteroid levels. Besides, we suggest that ecdysteroids exert a feed-back control on Lab idura gonadotrophic cycles.