6种舌鳎亚科鱼类ITS1序列长度多态性及系统分析

利用核糖体第一内转录间隔区(ITS1)对舌鳎亚科(Cynoglossinae)6种鱼类进行系统分析,发现舌鳎亚科ITS1区具有明显的序列长度多态性(404—744bp),序列长度分为三种类型,分别为404—405bp、462—463bp以及741—744bp,同一长度类型的不同种类间序列高度相似,平均遗传距离分别为0.00248、0.00217和0.00169,而不同类型间序列差异显著,平均遗传距离最小为0.38453。分析表明,序列长度多态性可能与物种分化时间有关。采用NJ(neighbour-joining)法及MP(maximum parsimony)法构建分子系统树,结合形态学特征及GenBank中的线粒体DNA序列进行分析,表明紫斑舌鳎(Cynoglossus purpureomaculatus)与短吻三线舌鳎(C.abbreviatus)可能为同物异名。另外,舌鳎属(Cynoglossus)的中华舌鳎(C.sinicus)与须鳎属(Paraplagusia)的日本须鳎(Paraplagusia japonica)聚为一支,舌鳎属中三线舌鳎亚属(Areliscus)的长吻红舌鳎(C.lighti)与拟舌鳎亚属(Cynoglossoides)的少鳞舌鳎(C.oligolepis)聚为一支,与形态分类学的观点不一致,值得进一步研究。

PHYLOGENETIC RELATIONSHIP AND LENGTH VARIATION IN THE FIRST RIBOSOMAL INTERNAL TRANSCRIBED SPACER OF CYNOGLOSSINAE SPECIES

Previous studies on phylogenetic relationship of Cynoglossinae fish species mostly on morphological data. However, the morphology-based plylogeny and classification of them remain controversial. Recently, combined with morphological data, large advancement has been made on molecular level and has yielded interesting results in regard to tonguefish taxa. In this study,the first ribosomal internal transcribed spacers (ITS1) of nuclear ribosomal DNA from six species of the subfamily Cynoglossinae were used for phylogenetic analysis. The significant length variation of ITS1 region was observed, with range of 404-744bp in length. Clade were established of three well-morphologically-defined groups. The first group, including C. purpureomaculatus and C. abbreviatus, was 404-405bp long; C. sinicus and P. japonica was, as the second group, in length of 462-463bp; and C. oligolepis and C. lighti, the last group, was 741-744bp long. The alignment length of ITS1 was 756 long, with variavle sites of 286, of which 285 were parsimony informative. High variabiligy was detected in the ITS1 region, and the conserved motifs were very short except for the motif (ACCCAACTCTCC), which was common for all species. The sequences contained relatively high GC content (from 66.2% to 69.5%), averaging 67.2%. The mean intra-group distance was 0.00248, 0.00217 and 0.00169 respectively, and the mean in-ter-group distances between Groups I and II was 0.3845, between II and III was 0.9088, and between I and III was 0.8685. The intra-group distances were very smaller than those of inter-group, suggesting that the species in the same group have very close relationship in evolution. The DNA data of these fishes were processed using neighbor-joining (NJ) and maximum parsimony (MP) methods to build phylogenetic relationships within the subfamily of them. Based on morphological, nuclear DNA and mitochondrial DNA data available so far, it is regarded that C. abbreviatus and C. purpureomaculatus could be the same species withe different morphs. Different from morphological taxonomy, C. sinicus of genus Cynoglossus and P. japonica (the only one species under genus Paraplagusia) were placed in a same clade with support of a high bootstrap value, and C. oligolepis and C. lighti were grouped in a clade together. More in-depth researches on more samples are suggested to further clarify the position of the fish taxonomy.