樹棲蛇類呼吸適應的探討

Abstract

特別細長的身體和向後縮短的血管肺腔都是樹棲蛇類為了因應樹上的生活所演化出來的有利特徵。這些形態生理的調適雖有諸多正面的好處，卻也可能因無效腔的延長而降低了呼吸的效率，我們因此推論樹棲蛇類的呼氣中二氧化碳的比率會較陸棲蛇類高。我們以本島產的大頭蛇和紅斑蛇分別代表樹棲和陸棲的蛇類，實驗前蛇都先經過二週的馴化，並控制食物，溫度和日週性，再以很合身的乳膠頭套套住頭部，由頭套前端的唯一的通氣口抽氣分析二氧化碳含量。結果顯示呼氣中二氧化碳的含量大頭蛇和紅斑蛇並無差異。否定了我們的假說。材料方法的改善，和其它影響蛇類呼吸效率的進一步探究，將有助於澄清樹棲蛇類呼吸適應的問題。

To adapt for arboreal life, tree-dwelling snakes have adopted many morphological changes. Among them, attenuated body shape and shortened vascular lung may induce certain drawbakcs that have never been discussed before. Both above traits may increase dead space and decrease the efficiency of carbon dioxide elimination. We predict the percentage of carbon dioxide in the expired air of arboreal snakes should higher than that of terrestrial snakes. Two species of snakes. Boiga kraepelini and Dinodon rufozonatum that represent arboreal and terrestrial snakes respectively were used in this test. Before test, the snakes were acclimated for two weeks. Other factors such as stomach content, diel cycle, ambient and body temperature were controlled. A Skin-tight flexible mask was made for each snake. Carbon dioxide content, analyzed by carbon dioxide analyzer CD-3A, was sampled from the expired air in a tube that was connected with the mask at the rostrum position. This tube was the only channel for respiration. We found that the carbon dioxide content of Boiga kraepelini and Dinodon rufozonatum has no significant difference. Therefore, the results contradicts our hypothesis. By improving material and method and/or inquiring more factors that affect respriatory efficiency will help to clarify our question.