Physiological and biochemical aspects of flight metabolism in cocoon-enclosed adults of the fruit beetle, Pachnoda sinuata.
We studied several aspects of flight metabolism in cocoon-enclosed adults of the fruit beetle Pachnoda to investigate their flight capability. The majority of adults which were forcefully removed from their pupal cocoon flew off within 5 min of exposure to bright sunlight. Most of the beetles which did not fly voluntarily were, however, capable of flight. Compared with 2-4 week old adults of the same species, cocoon-enclosed adults have higher reserves of glycogen in flight muscles and fat body, whereas the level of total carbohydrates in the haemolymph and the concentration of proline in haemolymph, flight muscles and fat body were similar.Enzymes involved in carbohydrate breakdown (MDH, GAPDH) were more active in flight muscles and fat body of cocoon-enclosed adults compared with adults, while enzymes of proline metabolism in the flight muscles (AlaT, NAD-ME) and fat body (AlaT, NADP-ME) had similar activities in cocoon-enclosed adults and adults. An enzyme of the beta-oxidation of fatty acids (HOAD) had similar activities in flight muscles and fat body of cocoon-enclosed adults and adults.Mitochondria isolated from flight muscles of adults removed prematurely from their cocoon favour the oxidation of proline and pyruvate. Pyruvate, however, is oxidized at higher rates than by mitochondria isolated from flight muscles of adults.During a short lift-generating flight, cocoon-enclosed adults proved that their flight muscles are capable of strong flight performance. During these flights, cocoon-enclosed adults consume proline and carbohydrates at a similar rate to that of adults.The endogenous AKH peptide, Mem-CC, has hyperprolinaemic and hypertrehalosaemic activity in cocoon-enclosed adults. The hypertrehalosaemic effect, however, is stronger in cocoon-enclosed adults than in adults.The content of Mem-CC in corpora cardiaca of larvae (3rd instar), cocoon-enclosed adults and 1 day-old adults is similar at 5-6 pmol per pair of corpora cardiaca, whereas it is higher in 10 day-old adults and 20 day-old adults (37 and 15 pmol per pair corpora cardiaca, respectively).From these results we conclude that cocoon-enclosed adults comply with all the prerequisites for flight performance before they leave their pupal cocoon. Furthermore, cocoon-enclosed adults have a more pronounced carbohydrate-based metabolism before they leave their cocoon compared with adults, which suggests that carbohydrate breakdown is mainly involved in such activities as leaving the cocoon and burrowing activity thereafter.
Auerswald
Lutz
L
Zoology Department, University of Cape Town, 7701, Rondebosch, South Africa
Gäde
Gerd
G