台灣地區克氏小丑魚顏色型與其族群遺傳研究

Abstract

克氏小丑魚(Amphiprion clarkii)是海葵魚亞科中分布最廣、可共生海葵種類最多、體色變異也最大的種類。其體色變異與地理區隔無關，但似乎與宿主海葵有所關聯。研究期間記錄到克氏小丑魚的宿主海葵共六種(n = 122)，其中黑色型的個體僅出現於莫氏列指海葵(Stichodactyla mertensii)中(n=17)，而一般型的個體偶見與黑色型個體出現於該種海葵之上(n=6)。在為期22天的野外移入實驗中，黑色型的個體在串珠異輻海葵(Heteractis aurora)上並沒有任何體色改變的傾向，且觀察到在莫氏列指海葵上的一般型個體，在70天之中亦無體色改變的傾向。在分子遺傳(粒線體DNA序列)及外部形質(鰭條軟條數)的分析顯示，黑色型與一般型的個體尚未有明顯的分化，且在野外觀察到在莫氏列指海葵上的一般型與黑色型個體有交配行為(2007年2~4月)。 先前針對日本的克氏小丑魚族群遺傳研究顯示，其族群可能受到洋流系統的影響而產生分化。本研究從台灣附近海域六個地區所採得的136隻個體，分析其粒線體D-loop區段序列。結果顯示，澎湖的族群與其他受黑潮影響的族群的分化程度已有顯著差異(Φst值= 0.044~0.088; p < 0.05)；而位於南中國海北部的東沙族群反而與墾丁、綠島、小琉球有一定程度的基因交流(Nm = 5.17~∞)。此結果顯示台灣地區克氏小丑魚的族群遺傳結構的確會受到洋流系統的影響，其中東沙族群非以往所認為受到南中國海水團影響較大；近年來對東沙附近的表層洋流研究也支持此一觀點。本研究建議將東沙族群與受黑潮所影響之族群歸類成同一地理系群，而與澎湖族群有所分別。

The Clark’s anemonefish, Amphiprion clarkii, is the most widely distributed, general symbiosis and variation of body color species in Amphiprioninae. Their coloration variation is not related to location, but seems to be related to host sea anemone. Here we recorded six species sea anemones symbiosis with A. clarkii (n = 122) in Taiwan. Individuals of the melanistic morph were found only on Mertens’ sea anemone, Stichodactyla mertensii, while individuals of the regular morph were rarely found on S. mertensii. To test the hypothesis that the melanistic morph might be induced by the sea anemone, we transplanted individuals (n =2) of the melanistic morph to the Beaded sea anemone, Heteractis aurora, and no color change was observed in 22 days, and we also observed one individual of normal morph no color change on S. mertensii in 70 days in the field. There was no meristic (fin rays counts) and genetic (mtDNA sequences) difference between two color morphs (n = 122). One case of hybridization between two color morphs was also observed in the field. Previous study of Japan’s population indicated that genetic structure of A. clarkii would be affected by different current system. Significant genetic differences (Φst value = -0.044~0.088) based on mitochondrial D-loop sequences were found among populations from six locations of Taiwan. The results of AMOVA showed that Penghu population was significantly different from other populations (Φst value = 0.044~0.088; p <0.05), while the Dongsha population was grouped with Kenting, Lutao and Xiaoliuchiu populations. This result suggests that the genetic structure of A. clarkii of Dongsha population was mainly affected by Kuroshio current. Overall, the population genetic structure of A. clarkii in Taiwan could be divided into 2 groups, Penghu population and those of the Kuroshio system including Kenting, Lutao, Xiaoliuchiu and Dongsha populations.