In vivo effects of Manduca sexta allatotropin and allatostatin on development and reproduction in the fall armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae)
U. Oeh et al., In vivo effects of Manduca sexta allatotropin and allatostatin on development and reproduction in the fall armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae), INVERTEBR R, 39(3), 2001, pp. 239-247
Two types of allato-regulating peptides, Manse-AT and Manse-AS, were inject
ed twice a day into larvae and adults of S. frugiperda to test their effect
s on life table parameters in vivo. Injections of Manse-AT (1 nmol per inje
ction) into penultimate instar larvae drastically reduced their weight gain
and increased mortality. The duration of the penultimate and the last larv
al stage, respectively, was prolonged in those animals which survived. Inje
ctions of Manse-AT (1 or 10 nmol per injection) into last instar larvae red
uced 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 deve
lopment of the animals, whereas combined injections of Manse-AS and Manse-A
T (1 nmol of each peptide) resulted in effects similar to those obtained wi
th Manse-AT alone. Peptide injections into adult female moths shortened the
ir life span and thereby reduced the total number of deposited eggs. The ov
iposition 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 fe
males did not affect juvenile hormone biosynthesis by the corpora allata ex
vivo. Incubation of Manse-AT with haemolymph from last instar larvae in vi
tro resulted in rapid degradation of the peptide with half-lives of 1 to 5
min.