溫度是影響外溫動物生理機能非常重要的因子，通常每一種動物生理反應都有其最佳的溫度範圍。隨著海拔升高，環境溫度逐漸下降，許多高海拔的外溫動物會改變其生理反應的最佳溫度範圍，以適應低溫環境。攝食與消化是動物能量來源的基礎，而偏好溫度（preferred temperature, PT），通常為一動物個體各種生理機能綜合表現較佳的溫度。在一些外溫動物，其偏好溫度通常也是攝食、消化與成長最佳的溫度。因此，本研究以台灣海拔分布廣泛的盤古蟾蜍（Bufo bankorensis）為材料，比較不同海拔族群攝食與消化的最佳溫度範圍，並探討其與偏好溫度之關係。本研究分為兩個章節。在第一章中，我測量馴化在不同溫度下，南仁山（海拔300 m）及阿里山（海拔2300 m）盤古蟾蜍的攝食能量（ingested energy, Ei）與消化效率（apparent digestibility coefficients, ADC），並且比較不同季節其表現是否有差異。第二章則測量馴化在不同溫度下，上述兩個海拔蟾蜍的PT，並探討 PT在日、夜和季節間的差異。結果發現，在攝食方面，南仁山族群冬季Ei的最佳表現溫度在22oC，夏季則在22-30oC。阿里山族群之Ei則隨溫度升高而增加。兩海拔蟾蜍在夏季的Ei均略高於冬季；僅南仁山族群馴養在22oC時，冬季高於夏季。而海拔族群間的差異只出現於冬季馴養在22oC時，南仁山蟾蜍的Ei高於阿里山。在消化方面，兩海拔盤古蟾蜍族群的ADC在馴養溫度內皆表現很高的效率（96-99%），並且隨馴化溫度上升而略微增加；但海拔間消化的差異並非表現在ADC，而是表現於低溫（15oC）馴養時的滯留時間（passage time）－冬季南仁山的蟾蜍在此溫度下整個消化過程比阿里山的蟾蜍多35天。在偏好溫度方面，（1）白天的PT隨著AT升高而增加，（2）在相同AT下，PT在日、夜間沒有差異，只有冬季馴化在22oC的阿里山族群，白天較夜晚偏好較高的溫度；且PT不會隨季節改變。（3）阿里山與南仁山蟾蜍的平均PT分別為22.46-26.69oC及19.86-24.42oC，阿里山蟾蜍族群白天的PT高於南仁山族群，但晚上的PT，與南仁山族群並無差異。綜合上述結果，南仁山族群在偏好溫度範圍內，Ei的確會有最佳的表現，且在此溫度區間內表現的比阿里山族群好。阿里山族群，Ei的最佳溫度是在測試溫度的最高溫（30oC），顯示若有較高的環境溫度，則會提升Ei的表現。但阿里山的環境中，很少有盤谷蟾蜍的偏好溫度。兩海拔蟾蜍族群之ADC在其偏好溫度範圍內皆有很好的表現。此外，阿里山蟾蜍在低溫下的食物滯留時間較短，有利於在高海拔低溫的環境迅速獲得能量。總結本篇的研究，南仁山的環境溫度較接近盤古蟾蜍的偏好溫度，故盤古蟾蜍可有最佳之攝食與消化表現；但阿里山的環境溫度低於盤古蟾蜍的偏好溫度，故盤古蟾蜍無法有最佳之攝食表現。若阿里山的盤古蟾蜍選擇白天溫度較高的微棲地，則有助於縮短食物通過消化道的時間，加快能量獲得的速率。

　　Temperature is the most important factor affecting the physiology performances of the ectotherms and each physiological function has an optimal temperature range. As elevation increases, environmental temperatures decrease. Many high-altitude ectotherms can alter the optimal temperature ranges in order to function better at the low temperature environments. Food intake and digestion are the essential processes for energy acquisition of organisms. Preferred temperature (PT) is a compromised set point for all physiological performances of an organism. In some ectotherms, food intake, digestion, and growth are maximized at PT. In this study, I use the common toads (Bufo bankorensis), which have wide altitudinal distribution in Taiwan, as a model to compare the optimal temperatures for food intake and digestion in different altitudinal populations, and to examine the relationship between PT and the optimal temperatures for food intake and digestion. In the first chapter, I measured ingested energy (Ei), food passage time, and apparent digestibility coefficients (ADC) in two altitudinal populations of Bufo bankorensis acclimated at different temperatures (15, 22 and 30oC). I also compared these indices in toads collected in winter and summer. In the second chapter, I measured PT of toads from two altitudes acclimated at 8, 15, 22, and 30oC. Furthermore, PT’s in different time of a day and seasons were also measured. The optimal temperature range (To) of Ei varied with season and altitudinal populations in Bufo bankorensis. In summer, the To of Ei for the lowland toads was 22-30oC, which was same as that for the high-altitude toads. In winter, To for the lowland toads was 22oC, but To was 30oC for the high-altitude toads. At low temperature (15oC), food passage time in the highland toads was shorter than that in the lowland toads indicating the turnover rate was faster in the high-altitude toads. ADC of Bufo bankorensis no matter in summer or winter remained rather constant at 96-99% between 15 and 30oC. The highland toads preferred slightly higher (in daytime) or same temperature (at night) than the lowland toads. PT in the lowland and high-altitude toads lacked seasonal variation. Day PT of the highland toads increased in winter when they were acclimated at 22oC. PT’s of the lowland and highland toads were 19.8-24.4oC and 22.5-26.7oC, respectively. In the lowland toads, the temperature range of their natural habitats is close to their PT and, at PT, the lowland toads can maximize their food intakes and ADC. In Alishan, the microhabitats having the toad’s preferred temperatures are probably limited and may reach the PT only in daytime when sunlight is available. However, at PT, food intake of the high-altitude toads increases with rising temperature in winter and reach maximum in summer. In addition, ADC is also maximized at PT in the highland toads. The highland toads have shorter food passage time and similar ADC to the lowland toads; therefore, they can gain energy faster at low temperature. In conclusion, the lowland toads live in habitats where food intake and digestion were maximized and PT is more attainable; however, the highland toads live in habitats where ambient temperatures are far from their PT and food intake is limited. However, if microhabitats with higher temperature in daytime are selected, food intake and digestion can speed up at high altitude.

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