Thermal sensitivity of oxygen uptake of Diptera from sub-Antarctic South Georgia and Marion Island

Abstract

Oxygen uptake of Paractora dreuxi (apterous) from Marion Island, which lies to the north of the Antarctic Polar Front, was compared to that of P. trichosterna (macropterous) and Antrops truncipennis (apterous) from South Georgia, which lies within the Antarctic Polar Front, over the range of temperatures experienced by these insects in their microhabitats. No differences in the slopes of log metabolic rate on temperature were found between the larvae of the two Paractora species, but the slope of the regression of log metabolic rate on temperature was steeper in the adults of P. trichosterna than in those of P. dreuxi. Therefore, metabolic cold adaptation was not found in P. trichosterna compared to P. dreuxi. However, some evidence for temperature compensation in A. truncipennis was found, although this could not be considered an adaptation. The difference in the thermal sensitivity of metabolic rate of the adults of the Paractora species is ascribed to differences in their life history strategies. Paractora trichosterna is a winged species in which retention of a thermal sensitivity similar to that of its larvae may facilitate resource location and so enhance fitness. On the other hand, the loss of flight in P. dreuxi may have allowed a reduction in thermal sensitivity that could mean a reduction in respiratory water loss at higher temperatures.