Link between elevated locomotor activity and the spike bursting of antennal thermosensitive neurons in the carabid beetle Pterostichus oblongopunctatus

Abstract

Many aspects of ectothermic life are affected by external temperature conditions. Therefore, thermosensation and thermoregulation are crucial for survival of ground dwelling carabid beetles. Research in sensory physiology with Pterostichus oblongopunctatus has shown change in the reaction of antennal thermoreceptor neurons at temperatures above the P. oblongopunctatus’s preferred temperature. From 25 °C, these neurons in dome shaped sensilla start to change from regular impulse firing to firing in bursts. We hypothesized that temperature-dependent impulse bursts are involved in P. oblongopunctatus’s behavioural thermoregulation. Behavioural experiments were carried out on the arena inside an environmental test chamber, and in two different temperature conditions – one with linearly increasing temperature, and the other with constant temperature. The temperature was increased from 10 °C to 40 °C linearly during 50 min on first case and with 5 degree steps on second case with duration 50 min each step. Locomotion parameters (velocity and travelled distance) were measured using an automated video tracking system. We observed both low and high activity zones in P. oblongopunctatus. The threshold temperature for changing between zones occurred was at 25.8 °C. This indicates a link between spike burst of antennal thermoreceptor neurons and behavioural thermoregulation in P. oblongopunctatus.