The Effects Of Thermal Environment And Food Availability On Functional Performance And Physiological Traits In Chinese Skinks [Plestiodon (Eumeces) Chinensis]

In this dissertation, I studied (1) the effects of thermal environment and food availability on selected body temperature, locomotor performance, testosterone and gonadal recrudescence; (2) seasonal acclimatization of locomotor performance and muscle metabolic enzymes in Chinese skinks[Plestiodon (Eumeces) chinensis]; The main results and conclusions are summarized as following:1. The effects of thermal environment and food availability on selected body temperature and locomotor performanceRemarkable temporal and spatial variations occur on selected body temperature (Tsel) and locomotor performance for the Chinese skinks [Plestiodon (Eumeces) chinensis]. The effects of thermal environment and food availability on Tsel and locomotor performance were determined in this study to elucidate the causes of these variations. Thermal treatments (4h and 8h) displayed significant effects on Tsel, additionally the effects of thermal treatment were also dependent on food-availability. There was no significant variation in skink's Tsel under diverse thermal treatments when sufficient food was available. However, with insufficient food source, the Tsel decreased with decrease in the duration of thermal treatment. Thermal acclimation also affected locomotor performance of P. chinensis, as the 8h thermal treatment enhanced their locomotor performance. However, food availability alone had no significant impact on the locomotor performance. Therefore, the combination of thermal acclimation and food availability could cause variations in Tsel and locomotor performance of skinks, suggesting that thermal environment and food condition in nature are important factors involved in temporal and spatial variations for Tsel and locomotor performance.2. The influence of thermal environment and food availability on testosterone and gonadal recrudescenceA two-factor experiment was carried out to determine the effects of thermal environments and food availability on growth in body mass, testosterone (T) levels and testes morphology in male P. chinensis. Skinks in the thermal environment mimicking spring (April) conditions grew slowly but had higher plasma T levels and larger testes with more viable sperms than those in the thermal environment mimicking summer (July) conditions. Skinks exposed to high food treatment grew faster and had higher plasma T levels and more viable sperms than those exposed to low food treatment. Male growth was negatively correlated with reproductive activity as indicated by T levels and testes size. Therefore, both temperature and food availability are important environmental factors that can affect the reproductive cycle of male lizards, and the mechanisms underlying the trade-off between growth and reproduction could involve the regulation of T levels.3. Seasonal acclimatization of locomotor performance and muscle metabolic enzymesThe locomotor performance, hematocrit and metabolic enzyme activity (lactate dehydrogenase, LDH) of P. chinensis were measured to reveal the seasonal acclimatization of behavioral and physiological traits in lizards. The locomotor performance of the skinks captured in spring was lower than that of the skinks captured in summer at body temperatures higher than 27℃, bud did not differ from each other at body temperatures lower than 24℃. The hematocrit was higher for P. chinensis at summer than at spring. The LDH activity of summer skinks was significantly higher than the spring skinks at 32℃, but did not differ at 22℃. Therefore, this trial demonstrated the existence of seasonal acclimatization in locomotor performance and physiological traits of Chinese skinks, which might be related to the seasonal difference of hematocrit and the seasonal acclimation of LDH activity.