https://scholars.lib.ntu.edu.tw/handle/123456789/45077
標題: | 福山魚怪的生活史與性轉變 | 作者: | 戴昌鳳 | 關鍵字: | Ichthyoxenus fushanensis;parasitism;sex change;selection | 公開日期: | 2000 | 出版社: | 臺北市:國立臺灣大學海洋研究所 | 摘要: | 福山魚怪屬於等足類係一新發現 之台灣特有種類,以一囊狀薄膜,成 對地寄生在台灣鏟頷魚腹腔。魚怪具 有先雄後雌的性轉變現象。本研究提 出「為何天擇有利於福山魚怪性轉變 的演化?」的可能解釋。 福山魚怪必需在短暫的幼生階 段尋獲並附著宿主,因此,其幼生階 段有很高的死亡率,僅很少數的幼生 能成功地與宿主形成寄生關係。高死 亡率使得天擇作用有利於能產生更多 子代的雌性。而雌性孕卵數則直接與 其體型大小呈正相關。雖然,福山魚 怪的雌雄個體體型大小均與宿主的體 型成正相關,但在排除宿主體型的影 響因子後,雌雄體型間則成負相關。 因此,在同一宿主之雌雄性別間,可 能存在著空間或食物上的競爭。這種 空間或食物上上的限制因素,導致雌 雄性體型上的互易作用(trade-off);亦 即,在一定體型的宿主內,越小的雄 性越有助於形成較大而且多產的配偶 雌性。此時,天擇將有利於先雄後雌 性轉換性的演化。 A flesh burrowing parasitic isopod, Ichthyoxenus fushanensis, was found infecting the body cavity of a freshwater fish, Varicorhinus bacbatulus, in pairs. The pattern of sequential hermaphroditism of I. fushanensis is protandrous. Here we investigate the question why selection favors protandrous sex change for I. fushanensis, through analyzing the interactions among clutch size, female size, male size and the host size. The number of young per brood was positively correlated with the body size of female. When the effect of host size is removed, there is a significant negative correlation between the sizes of paired males and females. This suggests that the resources available from host fish are limited, and that both larger female body size and smaller male body size are important determinants of Ichthyoxenus fushanensis offspring number. Due to the constraint of very low success rate in hunting for a host of mancas, the selection pressure favor larger female which produce more mancas. The pattern of interactions among host, male, female in size and the number of mancas, may be considered as a selection pressure for I. fushanensis, where the resource or available space is constrained by the size of host. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/14747 | 其他識別: | 892611B002001 | Rights: | 國立臺灣大學海洋研究所 |
顯示於: | 海洋研究所 |
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