Differences In Heat Tolerance And Physio-biochemical Mechanisms Between Female And Male Calliptamus Italicus Adults (Orthopera:Acrididae)

Calliptamus italicus is a major plague pest species in the arid and semi-arid grasslands of Xinjiang. Previous studies claimed that outbreaks of this pest were closely related to climate warming in Xinjiang since the 1980 s. This study aimed to explore differences in heat tolerance between adult females and males,including the physiological and biochemical mechanisms underlying these differences. The mortality, LT₅₀, LT90, free water/combined water, trehalose, soluble protein, oleic acid, linoleic acid, linolenic acid, SOD, POD and CAT enzyme activity content of females and males was measured after adults were placed into a climate cabinet under consistent temperature regimes of 27-51℃at 3℃ intervals for 4h.Mortality of females<42 and males℃ <39℃, the adult mortality rate less than 10%. At 48℃, the mortality of females and males were 38.83%, 51.17%, respectively, with temperature going up. The mortality of females and males were 100% at 51℃, LT₅₀ and LT90 of C. italicus females and males were 48.76℃, 47.90℃, 50.67 and 50.53℃ ℃, respectively. The contents of the six stress resistant substances of females and males showed a trend of first increasing,then decreasing, with temperature.Although the free water/combined water ratios of females and males were not significantly different under different temperatures（P>0.05）, their trehalose and oleic acid contents were significantly different（P<0.05）. The linolenic acid content of females and males was also significantly different（P<0.05） at all temperatures other than 42℃ and 45℃, and soluble protein content was also significantly different between the sexes（P<0.05） at all temperatures other than 27℃ and 48℃. There was no apparent regulation of the change in linoleic acid content.The enzyme activity of SOD, CAT in females and three kinds of enzymes of males showed a trend of first increasing, then decreasing, with temperature, enzyme activity of POD in females showed a trend of first decreasing, then increasing. Although the enzyme activity of SOD in females and males were not significantly different under different temperatures（P>0.05）, enzyme activity of POD in females and males were significantly different（P<0.05） at all temperatures other than 36℃, 42℃ and 48℃, enzyme activity of CAT in females and males were significantly different（P<0.05） at 27℃, 30℃ and 33℃.This study demonstrated that C.italicus can adapt to higher temperatures by regulating the contents of stress resistant substances and protection enzyme in certain temperature ranges, but from the contents of stress resistant substances and protective enzyme and growth rate comparison, the females response rate faster, showed that females had stronger ability of high temperature resistance.Based on results, it could predict that with the climate warming, C. italicus could shift to higher latitude and altitude areas,which would have a significant change in the early warning and predicting system and control decision-making.