通过Cyt b基因同源序列比较评估厦门文昌鱼的分类学地位

Taxonomic status of amphioxus Branchiostoma belcheri in Xiamen Beach estimated by homologous sequence of Cyt b gene

白氏文昌鱼Branchiostomabelcheri (Gray)在我国和日本沿海均有分布 ,由于南、北方文昌鱼形态学上有一定差异 ,且二者间存在一些过渡类型 ,其分类地位问题仍有待进一步澄清。本文测定了厦门欧厝海域产的文昌鱼mtDNACytb基因序列 ,并与日本产的文昌鱼以及另外产于大西洋的两种文昌鱼Cytb基因序列比较。分子系统学分析结果表明 :厦门欧厝海域产的文昌鱼与日本产的文昌鱼平均遗传距离为 2 1 12 % ,达到了种间分化的水平 ;经过对已有文献和文昌鱼地理分布的综合分析 ,作者建议将原来的白氏文昌鱼青岛亚种B belcheritsingtauense提升为种 ,南、北方所产文昌鱼分别作为两个独立的种存在 ,即南方的B belcheri (Gray)和北方的B

Branchiostoma belcheri(Gray)is distributed along the east coast of Asiatic mainland from South China Sea to Bohai Sea and Japanese waters.Scientists noticed morphological divergence between the animals from south to north area,and identified amphioxus in both Bohai Sea and Japanese waters as a new subspecies,B.belcheri tsingtauense.Nevertheless,intermediate forms between the southern and northern animals indicate their classification needs clarification.In the present research,we sequenced Cyt b gene of amphioxus sampled from Xiamen(Amoy)and compared the data with homologous sequences of Japanese amphioxus and two species living in the Atlantic Ocean.The results from molecular phylogenetic analysis showed that genetic distance between Xiamen amphioxus and Japanese amphioxus averages 21.12%with variation much above a normal species' divergence observed in other taxa.Considering the geographic,morphological and taxonomic records in the literature,we suggested that amphioxus in south and north areas might belong to different species and the original subspecies B.belcheri tsingtauense should be renamed as a separate species and its new scientific name should be B.tsingtauense Tchang et Koo,which includes animals both in Bohai Sea and in Japanese waters.Accordingly,amphioxus in Xiamen,including the animal distributed all south area,should keep the name of Branchiostoma belcheri(Gray).