oa African Entomology - Metabolic aspects of flight in the dung beetle Pachylomerus femoralis (Kirby) (Coleoptera: Scarabaeidae)
Concentrations of potential energy substrates were measured in the haemolymph and flight muscles of the dung beetle Pachylomerus femoralis (Kirby). Samples were taken from beetles at rest, captured during flight of unknown length, collected immediately after voluntary termination of flight (without any traces of dung in the vicinity) and collected immediately upon arrival at pats of fresh cattle dung in the Sandveld Nature Reserve, Free State Province, South Africa. Resting beetles had high concentrations of proline in the haemolymph (approximately 145/mol/ml) and flight muscles (approximately 70mol/g) but negligible concentrations of carbohydrates in the haemolymph (lower than 2 mg/ml) and glycogen in the flight muscles (approximately 0.l mol glucose equivalents/g). The beetles that were captured during flight, collected after they had terminated flight voluntarily or were trapped with fresh dung, had substantially lower proline levels in the haemolymph and flight muscles than resting beetles, while alanine levels in both compartments were significantly higher than in resting beetles. There were no differences in carbohydrate levels (in haemolymph and flight muscles) and lipid levels (haemolymph) between resting beetles and those that were active. From these results it was concluded that proline is the only energy substrate for flight in P. femoralis. Sufficient proline was available in the beetles each time it was measured. A lack of fuel is consequently not the reason for beetles to terminate flight.
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