Adipokinetic Neuropeptides and Flight Metabolism in Three Moth Species of the Families Sphingidae, Saturniidae and Bombycidae

Abstract

Methanolic extracts from corpora cardiaca of three moth species, Hippoteon eson (Sphingidae), Imbrasia cytherea (Saturniidae) and Bombyx mori (Bombycidae) show adipokinetic activity in conspecific bioassays. Haemolymph carbohydrates in these moths are not affected. These extracts are also active in heterologous bioassays: haemolymph lipids are increased in Locusta migratoria, whereas a small effect on haemolymph carbohydrates was observed in Periplaneta americana. Therefore, locusts can be used to monitor adipokinetic activity in corpora cardiaca from moth extracts during isolation. The three moth species possess an adipokinetic peptide with the same retention time on reversed phase high performance liquid chromatography (RP -HPLC) as a peptide isolated previously from Manduca sexta, which was code-named Mas-AKH. H. eson contains a second active peak with a similar retention time on RP-HPLC as the hypertrehalosaemic peptide isolated previously from Helicoverpa zea , code-named Hez-HrTH. Both synthetic peptides, Mas-AKH and Hez-HrTH, produce an adipokinetic effect in the three experimental moth species. In H. eson, the haemolymph concentration of Mas-AKH or Hez-HrTH needed to elicit a maximum hyperlipaemic response is about 20 to 30 nᴍ. Flight behaviour in the three moth species is quite different: H. eson is a good hovering flyer, I. cytherea is a comparatively bad flyer and B. mori males show only degenerate flight movements during their mating dance. Haemolymph lipid levels in H. eson decrease drastically during 15 min of flight and return to pre-flight levels in a subsequent rest period. The amount of lipids metabolized during flight is 10.9 mg/gxhr. Haemolymph carbohydrate levels drop during flight, but remain low during the 45 min of recovery. Haemolymph lipids in “dancing” males of B. mori remain constant. In individuals, however, which have low initial lipid levels in the blood, lipid concentrations increase significantly in a subsequent 15 min rest period after “dancing”. Metabolic changes during flight in I. cytherea were not investigated due to this species’ poor flight performance.