A NOVEL LOW-MOLECULAR-WEIGHT ECDYSIOTROPIN IN POSTDIAPAUSE, PREHATCH EGGS OF THE GYPSY-MOTH, LYMANTRIA-DISPAR L (LEPIDOPTERA, LYMANTRIIDAE)

Extracts of post-diapause, pre-hatch eggs of the gypsy moth, Lymantria dispar L. were examined for prothoracicotropic hormone (PTTH)-like ac tivity using an in vitro assay involving last-instar prothoracic gland s (PGs). The eggs were extracted in water, eluted from a low-pressure C-18-silica cartridge in 60 % acetonitrile, and fractionated on a high -performance, size-exclusion column. The primary ecdysiotropic activit y eluted with an estimated molecular weight of 2.1 kDa far below the 4 -7 kDa size determined for the low molecular weight PTTHs (bombyxins). Dose-response analysis revealed that the maximum activation was reduc ed by 75% by organic solvent extraction, but the remaining activity re tained the ability to maximally activate the PGs 10-fold in vitro. At least some of the ecdysiotropic activity in the post-diapause, pre-hat ch egg is localized in the brain of the pharate larva, and this activi ty increases dramatically prior to hatch when eggs are incubated at 25 degrees C.