In vivo effects of Manduca sexta allatotropin and allatostatin on development and reproduction in the fall armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae)

Two types of allato-regulating peptides, Manse-AT and Manse-AS, were injected twice a day into larvae and adults of S. frugiperda to test their effects on life table parameters in vivo. Injections of Manse-AT (1 nmol per injection) into penultimate instar larvae drastically reduced their weight gain and increased mortality. The duration of the penultimate and the last larval stage, respectively, was prolonged in those animals which survived. Injections of Manse-AT (1 or 10 nmol per injection) into last instar larvae reduced their weight gain and increased mortality in a dose-dependent manner. At the higher dose of 10 nmol no individual emerged. Injections of Manse-AS (1 nmol) into larvae of both larval stages hardly affected growth and development of the animals, whereas combined injections of Manse-AS and Manse-AT (1 nmol of each peptide) resulted in effects similar to those obtained with Manse-AT alone. Peptide injections into adult female moths shortened their life span and thereby reduced the total number of deposited eggs. The oviposition rate was reduced with Manse-AT alone and Manse-AS plus Manse-AT, whereas egg deposition in Manse-AS injected females on a per day basis was not affected during their short life span. Peptide injections into mated females did not affect juvenile hormone biosynthesis by the corpora allata ex vivo. Incubation of Manse-AT with haemolymph from last instar larvae in vitro resulted in rapid degradation of the peptide with half-lives of 1 to 5 min.