2-DEOXYECDYSONE IS A CIRCULATING ECDYSTEROID IN THE BEETLE ZOPHOBAS-ATRATUS

A qualitative analysis of ecdysteroids has been performed during the p ost-embryonic development of the tenebrionid beetle. Zophobas atratus, by high performance liquid chromatography (HPLC) combined with enzyme immunoassay (EIA) using two different antibodies. Three HPLC peaks we re found to be immunoreactive, in hemolymph extracts of both sexes. Mo reover, these peaks had ecdysteroid-like UV spectra, determined using a photodiode array detector. The use of two different HPLC systems (re verse and normal phases), in combination with two different EIA antibo dies, allowed us to identify 20-hydroxyecdysone (20E) and ecdysone (E) , as the two main ecdysteroids, but also suggested the presence of 2-d eoxyecdysone (2dE) as the third hemolymph component. Secretion of puta tive 2dE, together with E (but not 20E) was also demonstrated in vitro from incubations of prothoracic glands and of tegumental explants. In these experiments, either in vivo or in vitro, 3-dehydroecdysone was never observed. Our observations thus strongly suggest that 2dE is a c irculating ecdysteroid in Z. atratus and may function as a prohormone during the development of some insects.