INFLUENCE OF DEVELOPMENT AND PROTHORACICOTROPIC HORMONE ON THE ECDYSTEROIDS PRODUCED IN-VITRO BY THE PROTHORACIC GLANDS OF FEMALE GYPSY-MOTH (LYMANTRIA-DISPAR) PUPAE AND PHARATE ADULTS

Fluctuations in hemolymph ecdysteroid titer are part of a complex mech anism that regulates pupal-adult development. The amount of ecdysteroi d produced in vitro by prothoracic glands from female Lymantria dispar (L.) (Lepidoptera:Lymantriidae) pupae and pharate adults, as well as the competency of these glands to respond to a prothoracicotropic horm one (PTTH) stimulus in vitro, each correspond temporally with hemolymp h ecdysteroid titers. Based on studies of gland kinetics and dose-resp onses to brain extract using prothoracic glands from different female pupal and pharate adult ages, an in vitro bioassay for the quantificat ion of PTTH activity was developed using glands from day 2 females inc ubated without stimulus for 1 h followed by a 3 h incubation with stim ulus. Only extracts of brains and corpora allata from pupae and pharat e adults possess a PTTH factor, This factor is heat stable and can be separated on high performance size exclusion chromatography into two m olecular sizes of 13.75 and 3.2 kDa, Ecdysone and 3-dehydroecdysone ar e produced in vitro by prothoracic glands from all ages of female L. d ispar pupae and pharate adults tested. The amount of ecdysone produced by these glands exceeds that of 3-dehydroecdysone production after 4 h of incubation.