Effects Of Temperatures On Respiratory Metabolism And Enzyme Activities Of Gomphocerus Sibiricus(Orthoptera:Acrididae)

Gomphocerus sibiricus?L.?is a serious plague in alpine and subalpine meadow grasslands of Xinjiang.Previous studies have claimed that its outbreak is closely related to climate warming of Xinjiang.This paper aims to clarify the effect of temperature increasing on respiratory metabolism,five enzyme activities and discontinuous gas exchange cycles of G.Sibiricus.To explore stigma structure and the response of respiratory metabolism of G.Sibiricus to temperature stress,stigma structure was observed via scanning electron microscope?SEM?and O₂uptake rate,CO₂release rate,metabolic rate,respiratory quotient were measured via a multi-channel insect respiration apparatus?Sable Systems,USA?within a temperature gradient of 18-42?with 3?intervals.Results showed that G.sibiricus has ten pairs of circular,or near circular,shaped stigmata.Filter apparatus inside stigma were clustered.The respiratory metabolism of G.sibiricus first increased,then decreased.O₂uptake rates,CO₂release rates and metabolic rates of male and female adults at 18?were significantly lower than those at the other temperatures?P<0.05?;The respiratory metabolism of male and female adults underwent little change between 21 and 27?,which reveals that this temperature range is suitable for G.Sibiricus development.The RQ value we measured were from 0.9096-0.9961 and0.9039-1.0435 for males and females,and G.Sibiricus used carbohydrates as a substrate for respiratory metabolism in 18-42?.By using spectrophotometry with microplate reader,five enzyme activities including glyceraldehyde-phosphate?GAPDH?,glycerol-3-phosphate?GPDH?,lactate dehydrogenase?LDH?,3-hydroxyacyl-Co A dehydrogenase?HOAD?and citrate synthase?CS?of G.sibiricus were measured after being treated in Light Emitting Feed Box for 4 h without light condition within a temperature gradient of 18-42?with a 3?interval.The results showed that enzyme activities of G.sibiricus increased firstly and then decreased,with the values of males higher than those of females at the same temperature.The enzyme activities of both males and females minimized at 18?.The CS activities of females reached the maximum at 39?were 10.65±0.60 U/mg prot while the CS activity in males reached the peak at 36?were 9.78±1.24 U/mg prot.At different temperature,the enzyme activities between males and females were significantly different?P<0.05?except CS,and the ratios of GAPDH to HOAD were more than or close to 1.0.The carbohydrates were consumed for respiration at lower temperatures,while G.sibiricus used lipid and carbohydrates as energy substrates at higher temperatures.The third research aimed to determine the response of the discontinuous gas exchange cycle?DGC?duration in G.sibiricus to temperature stress,examined the DGC duration,interburst duration and burst duration of G.sibiricus adults by using Sable Systems from 18?to 36?with 3?intervals.The DGC duration,interburst duration and burst duration reached the peak at 18?were significantly higher than other tempeture?P<0.05?,and decreased with the increasing of temperature,reached minimized at 36??P<0.05?,male and female adults underwent little change between21 and 30??P>0.05?.This study demonstrated that G.sibiricus can change the intensity of respiratory metabolism,energy substrates and DGC duration for improving the capacity of adapting to the high temperature stress,which indicates the G.sibiricus is still a serious pest in Xinjiang under the trend of climate warming.