Physiological Responses Of Haemaphysalis Tibetensis To Environmental Changes

The tick Haemaphysalis tibetensis Hoogstraal,1965 is only distributed in Qinghai-Tibet in Tibet and Gansu province of China.It is an important pathogen vector in the Qinghai-Tibet Plateau.At present,the ecology,morphology,population dynamics,life cycle and molecular phylogeny of H.tibetensis have been investigated.However,the research on physiological adaptation mechanism to environment of this species is still absent.In order to elucidate the physiological responses of H.tibetensis to environmental changes,the effects of environmental changes on the contents of water and cold-hardiness substance of H.tibetensis have been conducted.For evaluating the adaptation strategies to the environmental stress and providing evidences for the analysis of the specific geographical distribution,the changes of antioxidant enzymes activity and MDA content were analyzed of H.tibetensis.The main results are as follows:1.Water: Compared with the wild population,the content of free water in the experimental population changed from 55.65% to 56.96%,although there is an upward trend,the difference is not significant.2.Cold-hardiness substance: Compared with the wild population,the contents of glycogen,fat and soluble protein in the experimental population significantly increased(P<0.05).The content of glycogen increased from 8.62 mg/g to 11.16 mg/g;fat increased from 16.39% to 21.66%;soluble protein increased from 1.06 gprot/l to 1.16 gprot/l.The content of glycerol in the hemolymph of the experimental population was significantly decreased from 12.21 ?g/ml to 10.81 ?g/ml(P<0.05).3.Antioxidant enzymes and malondialdehyde(MDA): With the development of H.tibetensis,the activity of antioxidant enzymes and the content of MDA were increased,the female ticks was the highest.Compared with the wild population,the activity of protective enzymes and the content of MDA in the experimental population increased significantly(P<0.05).The activity of superoxide dismutase(SOD)increased from 20.27 U/mgprot to26.06 U/mgprot;catalase(CAT)increased from 16.9 U/mgprot to 20.06 U/mgprot;peroxidase(POD)increased from 6.96 U/mgprot to 9.40 U/mgprot;the content of MDA increased from 12.35 nmol/mgprot to 14.48 nmol/mgprot.The activity of glutathioneS-transferases(GSTs)increased from 87.67 U/mgprot to 90.66 U/mgprot,although there was an increasing trend,the difference was not significant.4.Effects of temperature on antioxidant enzymes and MDA: Compared with the activities of antioxidant enzymes and the content of MDA of female H.tibetensis at 22?,the activity of SOD was significantly increased with the decrease of temperature(P<0.05),except 20?;CAT was significantly increased at-5? and 0?,but decreased at 10?(P<0.05);POD was significantly increased at-5?,0? and 5?(P<0.05);GSTs was significantly increased at-5?,and decreased at 5?,10? and 15?(P<0.05);the content of MDA was significantly reduced at 5?,10? and 15?(P<0.05).Under other temperatures,the activity of antioxidant enzymes and the content of MDA had no significant variation.