藤壺為固著性雌雄同體生物，大多行異體體內受精。異體交配時須利用長陰莖將精子送至另一個體之雌性腔室 (chamber) ，能夠跨越個體之間距離的長陰莖，是取得交配機會的重點，進而影響個體的生殖成功，因此擁有生物中比例最長的陰莖。但維持長陰莖需要相當高的成本，藤壺該如何決定陰莖長度的投資，並調整陰莖的長度？前人研究指出，海浪大小會影響加拿大某種藤壺的陰莖長度，顯示出物理性因子可以影響陰莖長度，而生物性因子是否也能影響藤壺的陰莖長度？本研究探討紋藤壺 (Balanus amphitrite) 個體之陰莖長度，是否可能依據所在位置的鄰居密度來做調整，藉此或許可以解釋種內陰莖長度的高度變異，而密度又以 (1) 鄰居有無 (2) 鄰居個數及 (3) 鄰居距離當作指標。首先自七股野外採集紋藤壺，隨機分配到不同處理組，進行45天的實驗，收集蛻殼並測量第三對和第六對觸手長度作為個體大小指標，並與陰莖長度做迴歸分析。實驗結果顯示，陰莖長度除了和個體大小有正相關之外，和鄰居的距離也有相關，且鄰居距離較遠時陰莖也顯著較長，但沒有發現陰莖長度和鄰居的個數有顯著差異，而沒有鄰居的紋藤壺陰莖長度較有鄰居組的還短。紋藤壺在有鄰居時，可能以最近鄰居的距離作為探測密度的指標，且在最近鄰居距離越近、密度越高時，因配偶數已夠多，比起密度低時，不需再增長陰莖以節省能量。而沒有鄰居的存在也就是密度低時，因碰不到鄰居便開始縮短或不投資陰莖，導致實驗結束時比起有鄰居組陰莖較短；此現象可能代表紋藤壺在沒有鄰居時，傾向於自體授精，減少或是不投資陰莖長度成為唯一的選擇。本研究結果支持紋藤壺陰莖長度的可塑性是一種天擇的結果。

Barnacles are mostly sessile, hermaphroditic, internal-fertilizing and usually non-selfing crustaceans. They have the longest penis length, relative to body length, among all organisms. Because of their immobility, barnacles have to extend penes to reach mates and transfer the sperm. The longer the penis the more mates they can reach. However, maintaining long penes may be costly. How do barnacles allocate the reproductive investment and adjust the length of penes? Previous researches indicated that wave actions influenced the penis length of barnacles. Here we explore if biological factors are also involved in determining the penis length. Our hypotheses are that the penis length of Balanus amphitrite may be determined by (1) the presence of neighbors, (2) neighbor numbers, and (3) neighbor distance. Experimental results indicate that the neighbor distance could influence the penis length of B. amphitrite, and the penis length increase with increasing distance of neighbors. The neighbor numbers were not found to influence the penis length. In the treatment of lone individuals, the penis lengths first increased and then decreased, and they are significantly shorter than those in the treatment with neighbors. When neighbors exist, B. amphitrite detects the density by distance of neighbors. The greater the distance to neighbors, the lower the densities of neighbors. Because of the mates are enough to mate, the penes length decrease with increasing density to save cost. When neighbors do not exist, B. amphitrite may save cost by decreasing or not investing pens length . Our result shows that the plasticity of the penis length of B. amphitrite is an adaptation by natural selection.

目錄
章次 頁數
壹、前言 1
貳、材料與方法 7
參、結果 10
肆、討論 15
參考文獻 21

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