Flight substrates and their regulation by a member of the AKH/RPCH family of neuropeptides in Cerambycidae

The pattern of metabolic changes during tethered flight with lift-generatio n was investigated in two South African species of long homed beetles (fami ly: Cerambycidae), namely Phryneta spinator and Ceroplesis thunbergi. Energ y substrates were measured in haemolymph and flight muscles at rest, after a flight period of 1 min at an ambient temperature of 25-29 degreesC, and 1 h thereafter. Flight diminished the levels of proline and carbohydrates in the haemolymph and proline and glycogen in the flight muscles of both spec ies, and caused an increase in the levels of alanine in both compartments. The concentration of lipids in the haemolymph, however, was not changed upo n flight in either species. The resting period of 1 h following a 1 min fli ght episode, was sufficient to reverse the metabolic situation in haemolymp h and flight muscles to pre-flight levels in both species. Purification of an extract of the corpora cardiaca from the two beetle species on RP-HPLC, resulted in the isolation and subsequently in the identification (by mass s pectrometry, Edman degradation and RP-HPLC) of an octapeptide of the AKH/RP CH family, denoted Pea-CAM-I (pGln-Val-Asn-Phe-Ser-Pro-Asn-Trpamide), prese nt in each species. It was demonstrated that low doses of Pea-CAM-I elicite d increases in the concentration of proline, as well as carbohydrates, in t he haemolymph of both species. The levels of lipids, however, remained unch anged upon injection of this peptide. It is concluded that, upon stimulatio n by flight, the peptide Pea-CAM-I is released from the corpus cardiacum of a cerambycid beetle and is responsible for the regulation of the major fli ght substrates, proline and carbohydrates, of these beetles. (C) 2000 Elsev ier Science Ltd. All rights reserved.