Comparison Of Thermal Tolerance,Antioxidant Capacity And HSP70 Expression Between Invasive Trachemys Scripta Elegans And Native Turtles

The red-eared slider(Trachemys scripta elegansis)is an exotic species that has a very wide range of invasions and seriously endangers the local ecological environment and economic development.For oviparous reptiles,environmental temperature has an important effect on embryonic development,morphological characteristics,thermal tolerance,and geographical distribution.Heat shock proteins(HSPs)are a class of proteins that play a molecular chaperone role after organism is subjected to stress.Studies have shown that the expression level of HSPs in animals is closely related to their thermal tolerance.In this study,we used T.scripta elegansis,Ocadia sinensis,Mauremys mutica and Mauremys reevesii as the experimental subjects.We compared the effects of incubation temperature and acclimation temperature on the body weight,antioxidative enzyme activity,malondialdehyde content,thermal tolerance,relative expression of HSP70 mRNA in these 4 species of turtles and compared the effects of latitude on morphological characteristics,thermal tolerance,and relative expression of HSP70 mRNA in these 4 species of turtles.Finally,we discuss the physiological and biochemical basis and molecular mechanism of the T.scripta elegansis invasion.The main results are as follows:(1)Incubation temperature(24?,28?,32?)had a significant effect on relative expression of HSP70 mRNA in embryo,liver CAT activity,hatchling weight,low-and high-temperature tolerance in our 4 species of turtles.However,there was no significant effect on SOD activity,MDA content and thermal resistance range of hatchlings.Turtle hatchlings from 32? had the lowest weight.Turtle hatchlings from 24? had relatively better low-temperature tolerance,while those from 32? had the best high-temperature tolerance.The CAT activity in the liver of hatchlings was low at 32?.The relative expression of HSP70 mRNA was highest at 32? in O.sinensis and M.reevesii,but M.mutica was the lowest,while the T.scripta elegans was the highest at moderate temperature(28?).The relative expression levels of HSP70 mRNA in four species of turtle embryos were significantly different at different embryonic stages(1/3,1/2,and 2/3 phases)with being higher at later.The relative expression of HSP70 mRNA in the liver of O.sinensis hatchlings from 32? was higher,whereas M.mutica hatchlings from 28? was highest.In T.scripta elegans,the relative expression levels of HSP70 mRNA was the highest at 24? and lowest at 32?.There were significant differences among the four species of turtles in terms of birth weight,critical thermal minimum,critical thermal maximum and thermal resistance range,liver CAT activity and MDA content.However,the difference in SOD activity in the liver was not significant.T.scripta elegans had the highest birth weight,and M.reevesii had the lowest birth weight.T.scripta elegans and M.reevesii were better tolerated at low temperatures than O.sinensis and M.mutica.T.scripta elegans had better high-temperature tolerance and greater thermal resistance range than the other three native turtle.The content of MDA in the liver was relatively low in T.scripta elegans and O.sinensis,and the activity of CAT in the liver was the lowest in T.scripta elegans.(2)Acclimation temperature(17?,25?,33?)had a significant effect on the body weight,critical thermal minimum,critical thermal maximum and thermal resistance range,but not on the SOD activity,CAT activity and MDA content in the liver of hatchlings.After being acclimated at 17?,hatchling turtles had the best low-temperature tolerance.After being acclimated at 33?,hatchling turtles had better high-temperature tolerance and a wider thermal resistance range.Acclimation temperature had a significant effect on the relative expression of HSP70 mRNA in the livers in T.scripta elegans and O.sinensis,but not in M.mutica and M.reevesii.The relative expression of HSP70 mRNA was lowest at 17? in the liver of O.sinensis.And as for the livers of T.scripta elegans,the highest value was at 17? and lowest was at 33?.There were significant differences among four species in body weight,critical thermal minimum,critical thermal maximum and thermal resistance range,liver SOD activity and CAT activity after acclimation,but no difference in MDA content between species.The acclimated body of T.scripta elegans and O.sinensis was larger than that of the M.reevesii and M.mutica.M.reevesii had the best tolerance at low temperatures.O.sinensis,T.scripta elegans and M.reevesii had better high-temperature tolerance and greater thermal resistance range than M.mutica.The activity of SOD in the liver of T.scripta elegans and M.mutica was relatively high,and the activity of CAT in the liver of T.scripta elegans was the lowest.(3)In general,low-latitude cultured groups of 4 species of turtles had higher body weight,longer carapace length,width and height than those cultured at high latitudes.Low-latitude cultured populations had better tolerance to high temperatures and poor tolerance at low temperatures.However,high-altitude cultured groups had the opposite effect.Low-latitude cultured groups have greater thermal resistance range.Heat shock temperature had a significant effect on the relative expression of HSP70 mRNA in the liver of 4 species of turtles.After heat shock treatment,the relative expression of HSP70 mRNA was highest in the liver of O.sinensis at 35?.And as for the livers of T.scripta elegans and M.reevesii,the highest value was at 15? and lowest was at 25?.