Immunocytochemical localization of an allatotropin in developmental stages of Heliothis virescens and Apis mellifera

Juvenile hormone biosynthesis by the corpora allata is regulated by stimulatory neuropeptides called allatotropins and inhibitory neuropeptides called allatostatins. This study localized Manduca sexta allatotropin-like material in developmental stages of the noctuid moth Heliothis virescens and the honeybee Apis mellifera. Immunocytochemical methods using both fluorescence-tagged antibodies and enzyme-coupled antibodies were used to stain the central nervous tissue of both species. H. virescens contains M. sexta allatotropin (Manse-AT)-like material consistently throughout larval development. The distribution patterns of Manse-AT immunoreactive cell bodies in the CNS persisted from one larval instar to the next. It will be discussed how larval Manse-AT distribution patterns differed from those in adults. The total number of AT-containing cells in brain and subesophageal ganglion gradually increased during larval development, whereas in the thoracic and abdominal ganglia, the number of AT-containing neurons remained constant. In the honeybee A. mellifera, Manse-AT immunoreactive cells were only found in a few brains from late last instar larvae (prepupae). Manse-AT-like material was present in a group of 6-8 cells in the pars intercerebralis. However, we did not find any Manse-AT-like material in brains of early last instar larvae, whose corpora allata (CA) are more sensitive to in vitro stimulation by Manse-AT than prepupal CA.