A Comparison Of Temperatures Effects On Hatchling Phenotypes,Physiology And Functional Performance Between Two Turtles,Trachemys Scripta Elegans And Mauremys Reevesii

The invasion of alien species has been one of important risk factors that affected biodiversity and ecosystem.The knowledge of locomotor capacity and physiological basis of alien species is a critical key to understand the invasion mechanism and to propose administration measures for prevention and control.Trachemys scripta elegans has been listed as one of the world's most dangerous invasive species.It has brought huge ecological crisis in China.In this study,the invasive turtle species T.scripta elegans and a native species Mauremys reevesii were used to compare:(1)the effects of incubation temperature on embryonic development and hatchling phenotypes between the two species;(2)the effects of acclimation temperature on locomotor capacity and thermal tolerance between the two species.We collected T.scripta elegans and M.reevesii eggs from two geographical cultured populations(Haikou and Haining),and hatched them at three constant temperatures(24,28 and 32?C).Our results showed that egg mass of T.scripta elegans was heavier than that of Mauremys reevesii,but there was no difference in eggs size between different cultured populations.The incubation periods of both species decreased with the increasing incubation temperatures.T.scripta elegans eggs have a longer incubation period in 24?C,but similar in 28?C,and shorter than M.reevesii in 32?C.Hatchling body mass of T.scripta elegans was larger than that of M.reevesii at three temperatures.Hatchling body mass of high-latitude turtles was larger than that of low-latitude ones in 24?C,but it's opposite in 28 and 32?C.The effect of incubation temperature on embryonic heart rate differed between different species and among developmental stages.For example,the heart rate of M.reevesii embryos was faster than that of T.scripta elegans embryos at relatively lower incubation temperatures,but slower at higher incubation temperatures.Generally,test temperature had a significant effect on locomotor performance(righting time and swimming speed)and heart rate of hatchlings.The heart rate of T.scripta elegans hatchlings was faster than M.reevesii hatchlings,but was not different between cultured populations.Hatchling righting performance did not differ between species and among incubation treatments.It seemed that the swimming speed of hatchlings from moderate temperature was faster than from higher or lower temperatures.T.scripta elegans hatchlings swam faster than M.reevesi hatchlings,but no inter-population difference was observed.Thermal tolerance of T.scripta elegans hatchlings was greater than that of M.reevesi hatchlings at each incubation temperature.Generally,temperature acclimation had a significant effect on locomotor performance(righting time and swimming speed)and thermal tolerance of hatchling turtles.The righting time of high-acclimated T.scripta elegans hatchlings was shorter than that of low-acclimated ones,but it did not differ among different acclimation treatments in M.reevesi.Low-latitude hatchlings had a shorter righting time than highlatitude ones in both turtle species.The swimming speed of T.scripta elegans hatchlings was greater than that of M.reevesi hatchlings at each acclimation temperature,but it did not differ between cultured populations.The effect of acclimation temperature on hatchling thermal tolerance differed between species and between cultured populations.For example,the critical thermal maximum(CTMax)increased with the increasing acclimation temperatures in T.scripta elegans,but was greatest at intermediate acclimation temperature in M.reevesi.Low-latitude hatchlings had a better ability of low-temperature resistance at low acclimation temperature,but high-latitude hatchlings at intermediate acclimation temperature.