Feeding impairs chill coma recovery in the migratory locust (Locusta migratoria)

Low temperature causes loss of neuromuscular function in a wide range of insects, such that the animals enter a state known as chill coma. The ability to recover from chill coma (chill coma recovery time) is often a popular phenotype to characterise chill tolerance in insects. Chill coma in insects has been shown to be associated with a decrease in haemolymph volume and a marked increase in K⁺], causing dissipation of K⁺ equilibrium potential and resting membrane potential. High potassium diet (wheat) has also previously been shown to increase haemolymph K⁺] in Locusta migratoria leading to sluggish behaviour. The present study combined these two independent stressors of ion and water homeostasis, in order to investigate the role of K⁺- and water-balance during recovery from chill coma, in the chill sensitive insect L. migratoria. We confirmed that cold shock elicits a fast increase in haemolymph K⁺] which is likely caused by a water shift from the haemolymph to the muscles and other tissues. Recovery of haemolymph K⁺] is however not only reliant on recovery of haemolymph volume, as the recovery of water and K⁺ is decoupled. Chill coma recovery time, after 2 h at −4 °C, differed significantly between fasted animals and those fed on high K⁺ diet. This difference was not associated with an increased disturbance of haemolymph K⁺] in the fed animals, instead it was associated with a slowed recovery of muscle K⁺], muslce water, haemolymph Na⁺] and K⁺equilibrium potential in the fed animals.