Latitudinal Variation And Underlying Mechanisms Of The Developmental Plasticity In Embryonic Heat Tolerance Of North Grass Lizards (Takydromus Septentrionalis)

Anthropogenic global warming(AGW)has imposed significantly negative impacts on animals.However,the effects of climate warming on animals varied latitudinally.By now most of the researches about effects of climate warming on animals focus on the adult stage of animals,leaving the responses of embryos remain obscure.In this study,we used different latitudinal populations of a widespread grass lizard(Takydromus septentrionalis)as subjects,incubated the eggs of each population at 24?,28? and 32? respectively.On the halfway of the incubation,we compared the surface and core thermal tolerance,thermal sensitivities of heart rate,egg mass,embryonic mass,water ratio of eggs and embryos at different temperatures from the three populations.We aim to(1)reveal the latitudinal pattern of thermal tolerance in heat tolerance of embryos;(2)reveal the latitudinal pattern of developmental plasticity in embryonic heat tolerance;and(3)potential physiological and bio-physical mechanisms of embryonic heat tolerance.The results show that surface and core heat tolerances were enhanced as the latitudes increasing,while the thermal sensitivities of heart rates decreased as latitudes increasing.The embryos of the low-latitude population had lower heat tolerance as the incubation temperature increasing,and the embryos of the mid-latitude population had poor heat resistance at both high and low temperatures,whereas incubation temperature had no obvious effects on the embryos of the high latitude population.The embryos from the low latitude population had the lowest egg weight,embryo weight,egg shell thickness,and water content in eggs among the three geographical populations.The results show that the performance of mid-latitude and high-latitude embryos is similar in terms of egg mass,embryo mass,egg shell thickness,and water content in eggs,while low-latitude embryos perform worse in these features than mid-high latitude embryos,resulting in a significantly lower thermal tolerance in low-latitude embryos than mid-high latitude embryos.This study reveals the significant role of embryonic heat tolerance in the responses to climate warming,and the underlying physiological and bio-physical mechanisms.These results would widen our knowledge of the response of animals to climate warming and therefore form theoretical basis of animal conservation in the context of climate warming.