| Abstract: | 全球雨水酸化日愈嚴重，亞洲地區有62%的地區有雨水酸化的情形，對水生動物的生理造成影響。兩棲類蝌蚪因具有高通透性與濕潤的皮膚且侷限在水體中而容易面臨酸壓力的影響。前人實驗研究發現，受酸處理的蝌蚪體重和成長率下降，而野外棲地酸化導致蛙類族群量下降甚至消失。然而，大多數研究探討酸對開放性水域(如水池、溪流)兩棲動物生理的影響，但較少關注封閉性且低緩衝的棲地如容器性積水棲地(container habitats); 此種棲地的蛙類可能更先面臨酸雨的威脅。因此，本實驗目的探討酸對生活於容器性積水蝌蚪的存活率、成長、發育以及高溫耐受(CTmax)的影響。實驗物種為艾氏樹蛙(Kurixalus eiffingeri)、翡翠樹蛙(Rhacophorus prasinatus) 和布氏樹蛙(Polypedates braueri)，其蝌蚪棲地或部份為容器性積水棲地。我從野外採集這三種蝌蚪，將其帶回實驗室，進行七天的馴養，然後測量存活、成長發育與高溫耐受度(CTmax)。結果發現，酸對於蝌蚪存活率的影響有劑量反應的情況，在越酸的組別中存活率越低。在三種物種中，艾氏樹蛙蝌蚪的耐酸性最高。此外，酸對存活蝌蚪成長發育的影響有種間差異: 酸會影響布氏樹蛙的成長與發育但翡翠樹蛙則不受影響，而艾氏樹蛙只有成長會受到酸的影響。此外，酸只對艾氏樹蛙蝌蚪的CTmax造成影響。酸對不同種蝌蚪造成差異性影響可能與棲地pH值有關，這可能部份解釋為什麼K. eiffingeri 有較好的酸耐受。從細胞階層來看，酸耐受的種間差異可能與物種鈉離子含量有關，而蝌蚪的成長與發育受酸影響而下降，可能與鈉離子失衡、能量權衡或覓食行為減少相關。最後，容器性積水棲地蝌蚪的酸耐受和利用非容器性水體繁殖的物種(澤蛙和拉都希氏赤蛙)的酸耐受沒有差異，這比較結果暗示，當未來酸雨變得更加嚴重時，存活於低緩衝棲地的布氏樹蛙和翡翠樹蛙可能在未來會面臨更大的壓力。
Global acid precipitation is a serious issue, in Asia, about 62 percent of rainwater is pH< 5.0. Acid rain causes water acidification which affects the physiology of aquatic animals. Amphibians with high permeability and moisture skin are susceptible to the acidification of the water bodies. Tadpoles which are restricted in water bodies are even more vulnerable to acidic stresses. Previous studies found that acidic environments prolonged the development of frog embryos and reduced body mass and growth rate of tadpoles. Acidic habitats caused local populations to decline or even disappear. However, most of the previous studies investigated the influence of acid on the physiology of amphibians in opened water habitats (such as ponds and rivers), but less focused on closed, poorly buffered habitats such as container habitats, which might face greater pressures in the case of water acidification. Therefore, the purpose of this study was to assess the acid effects on the survival rate, growth, development, and critical thermal maximum (CTmax) of tadpole living in the container habitats. Study species are Kurixalus eiffingeri, Rhacophorus prasinatus and Polypedates braueri, and their tadpoles live in container habitats such as bamboo stumps or water tanks. I subjected tadpoles to pH 3.5 to 7 to monitor survivorship. I also monitored the growth and development of surviving tadpoles for 7 days, and measured CTmax. Results showed that the effect of acid on the survival rate of tadpoles are dose-responsive, the survival rate of tadpoles decreased as pH decreased. Kurixalus eiffingeri have higher tolerance among three species. Results also showed that interspecific variation in acidic effects on growth and development of tadpoles: the growth and development of P. braueri were affected by acid, but R. prasinatus were not. In K. eiffingeri, only the growth of tadpoles was affected by acid. Finally, only CTmax of K. eiffingeri tadpoles were affected by acid. Interspecific variation in acidic effects on tadpoles may be related to habitat pH which may explain why K. eiffingeri has better acid tolerance than other species. In the cellular basis, interspecific variation in acid tolerance may relate to sodium ion regulation. The growth and development of tadpoles are affected by acid which may be related to sodium ion imbalance, energy trade-off and/or reduced foraging behavior. Finally, acid tolerance of P. braueri and R. prasinatus are not different from pond or stream breeders (Ferjervarya limnocharis and Hylarana latouchii). These findings suggest that P. braueri and R. prasinatus, live in the low buffered habitats, may face greater stress as the acid rain becomes more serious in the future. |
