Meeting Abstract

P3.159  Sunday, Jan. 6  Neural control of gas exchange pattern is phase-dependent in the desert locust GEFEN, E.*; BERMAN, T.S.; University of Haifa- Oranim, Israel gefene@research.haifa.ac.il

The adaptive significance of discontinuous gas-exchange cycles (DGC) in insects is contentious. The recently proposed neural hypothesis suggests that DGC is expressed when insects conserve energy by reducing brain activity at rest, thus releasing thoracic ganglia from descending control of ventilatory activity. In accordance with this hypothesis, we predicted that the highly-responsive sensory pathways and considerably larger brain size in gregarious compared with solitary Schistocerca gregaria locusts would be reflected in higher DGC prevalence at rest in the former. Furthermore, cutting the connectives between the head and thoracic ganglia was expected to result in disappearance of phase-dependent variation in gas-exchange patterns, as well as in an overall increase in DGC expression. We used flow-through respirometry at 30^ºC for measuring metabolic rates (MR) and gas-exchange patterns in intact, connective cut (CC) and sham-operated adult male locusts of both density-dependent phases. DGC was not more common in gregarious locusts, although results may have been confounded by their significantly higher MR in comparison with solitary locusts. However, severing the connectives between head and thoracic ganglia did not increase DGC expression in gregarious locusts. Moreover, DGC was abolished altogether in CC solitary individuals, which switched to a distinctly continuous gas-exchange pattern (surgical treatments did not affect MR). These results are not consistent with predictions of the neural hypothesis, based on brain inhibitory effect on ventilatory centers in thoracic ganglia. Furthermore, a significant difference in DGC expression between gregarious and solitary CC locusts may point at neural plasticity of ventilatory control.