Effect of thermal acclimation on thermal preference, resistance and locomotor performance of hatchling soft-shelled turtle

The significant influence of thermal acclimation on physiological and behavioral performance has been documented in many ectothermic animals, but such studies are still limited in turtle species. We acclimated hatchling soft-shelled turtles Pelodiscus sinensis under three thermal conditions （10, 20 and 30~C） for 4 weeks, and then measured selected body temperature （Tsel）, critical thermal minimum （CTMin） and maximum （CTM^x）, and locomotor performance at different body temperatures. Thermal acclimation significantly affected thermal preference and resistance of P sinensis hatchlings. Hatchling turtles accli- mated to 10~C selected relatively lower body temperatures and were less resistant to high temperatures than those acclimated to 20~C and 30~C. The turtles＇ resistance to low temperatures increased with a decreasing acclimation temperature. The thermal re- sistance range （i.e. the difference between CTM^x and CTMin, TRR） was widest in turtles acclimated to 20~C, and narrowest in those acclimated to 10~C. The locomotor performance of turtles was affected by both body temperature and acclimation tem- perature. Hatchling turtles acclimated to relatively higher temperatures swam faster than did those acclimated to lower temperatures. Accordingly, hatchling turtles acclimated to a particular temperature may not enhance the performance at that temperature. Instead, hatchlings acclimated to relatively warm temperatures have a better performance, supporting the ＂hotter is better＂ hypothesis.

The Seasonal Acclimatisation of Locomotion in a Terrestrial Reptile, Plestiodon chinensis(Scincidae)

Studies of the seasonal acclimatisation of behavioural and physiological processes usually focus on aquatic or semi-aquatic ectotherms and focus less effort on terrestrial ectotherms that experience more thermally heterogeneous environments. We conducted comparative studies and thermal acclimation experiments on the locomotion of the Chinese skink （Plestiodon chinensis） to test whether seasonal acclimatisation in locomotion exists in these terrestrial ectothermic vertebrates, and whether seasonal acclimatisation is predominantly induced by thermal environments. In natural populations, skinks ran faster during the summer season than during the spring season at high-test temperatures ranging from 27℃ to 36℃ but not at low-test temperatures ranging from 18℃ to 24℃. In contrast, the thermal acclimation experiments showed that the cold-acclimated skinks ran faster than the warm-acclimated skinks at the low- test temperatures but not at high-test temperatures. Therefore, the seasonal acclimatisation occurs to P chinensis, and may be induced by temperature as well as other factors like food availability, as indicated by the seasonal variation in the thermal dependence of locomotion, and the discrepancy between seasonal acclimatisation and thermal acclimation on locomotion.

Metabolic enzymes in seasonally acclimatized and cold acclimated rufous-collared sparrow inhabiting a Chilean Mediterranean environment

Due to the higher energy requirements of birds during winter, it is predicted that the activities of metabolic enzymes （e.g., citrate synthase, CS and cytochrome C oxidase, COX） should increase in tandem with increases in rates of energy expendi ture （e.g., basal metabolic rate, BMR）. However, there is mixed support for the hypothesis of enzymatic acclimatization. Fur thermore, there is little information about the effect of ambient temperature on energetics and tissue enzyme activity levels in passerines inhabiting seasonal Mediterranean environments. In this study we evaluated the interplay between BMR and enzyme activities of freshly caught individuals of the passerine Zonotrichia capensis in winter and summer in a Mediterranean environment from central Chile, and also in warm （30℃） and cold （15℃） labacclimated birds. The results revealed a lack of seasonal variation in BMR, thermal conductance and in the activity of CS and COX. However, we found higher BMR and lower thermal conductance in coldacclimated than in warmacclimated birds. Also, total CS activity was higher in the flight muscles of coldacclimated than in warmacclimated birds. We found also a significant correlation between BMR and total CS activity in pectoral muscle. Although some authors have suggested that BMR mainly depends on the metabolic intensity and mass of internal organs, our results revealed that skeletal muscles such as the flight muscles may also affect BMR. Finally, differences in the accli mation and acclimatization responses in Rufouscollared sparrows suggest that largescale oscillations in the physical environment might maintain the capacity for flexibility in thermogenic traits through generations .

Long-term warming does not affect soil ecoenzyme activity and original microbial nutrient limitation on the Qinghai-Tibet Plateau

Microbes play an important role in the carbon cycle and nutrient flow of the soil ecosystem.However,the response of microbial activities to long-term warming over decades is poorly understood.To determine how warming changes ecoenzyme activity and microbial nutrient limitation,we conducted a long-term,21 years,experiment,on the Qinghai–Tibet Plateau.We selected typical grass-and shrub-covered plots,used fiberglass open-top chambers(OTCs)to raise the temperature,conducted soil sampling at different depths,studied the response of nutrient-acquiring enzyme activity and stoichiometry,and conducted vector analysis of stoichiometry.Our results showed that long-term warming did not have a notable effect on the activity of nutrient-acquiring enzymes or enzymatic stoichiometry.However,Spearman correlation analysis indicated a significant and positive correlation between ecoenzyme activity and the available nutrients and microbial biomass in soil.Vector analysis of stoichiometry showed phosphorus limitation for all soil microbes at different depths,regardless of whether the soil experienced warming.These changes in enzymatic stoichiometry and vector analysis suggested that microbial nutrient limitation was not alleviated substantially by long-term warming,and warming did not considerably affect the stratification of microbial nutrient limitation.Our research has also shown that long-term warming does not significantly change soil ecoenzyme activity and original microbial nutrient limitation at different soil depths within the OTUsʼimpact range.These results could help improve understanding of microbial thermal acclimation and response to future long-term global warming.