A comparative study on hypertrehalosaemic hormones in the Hymenoptera: sequence determination, physiological actions and biological significance.
A new hypertrehalosaemic peptide (Tea-HrTH; pQLNFSTGWGG-NH(2)) was isolated from the corpora cardiaca (CC) of the sawfly Tenthredo arcuata. The hypertrehalosaemic peptides found in the CC of five Bombus species and the paper wasp Polistes fuscata were identical to the adipokinetic hormone II of the desert locust, Schistocerca gregaria (Scg-AKH-II). The hypertrehalosaemic peptides found in the yellowjacket Vespula vulgaris and the hornet Vespa crabro were identical to the adipokinetic hormone of the cricket, Gryllus bimaculatus (Grb-AKH).All species examined had a large storage crop which, when filled with honey, held up to one-third of their total body weight. Overwintering queens of P. fuscata had large stores of carbohydrates and lipids in the abdomen, and were able to survive months of fasting. Workers of Bombus hortorum (bumble-bee), Apis mellifera (honey-bee) and V. vulgaris had little or no fat body. These species could fly as long as sugar was present in their crops, but they stopped flying as the carbohydrates in the crop disappeared. There was no significant increase in the haemolymph carbohydrate titres after injections of CC extracts or corresponding synthetic peptides into workers of B. hortorum or into males and females of T. arcuata. There was a moderate increase in haemolymph carbohydrate titres when these peptides were injected into overwintering queens of P. fuscata and into workers of V. crabro, both with significant amounts of fat body. However, well-fed V. vulgaris workers, with very little fat body, also responded to their own hypertrehalosaemic peptide.