PRELIMINARY STUDY ON MITOCHONDRIAL CYTOCHROME b DNA SEQUENCES AND PHYLOGENY OF FORMALIN FIXED SISORID FISHES(Teleostei: Siluriformes)

从９种科鱼类的福尔马林标本中获得了３３３ｂｐ的细胞色素ｂ基因片段的序列。这９个种分别代表科鱼类的８个属。３３３ｂｐ的ＤＮＡ序列经ＭＵＳＴ软件排序后，有１０１个变异位点，其中有３９个信息位点。序列在成对物种间的距离为８～４８。平均遗传距离为２４％～１４４％。简约分析产生了最大简约系统树，其步长是１６２（ＣＩ＝０７３５，ＲＩ＝０４９４）。在该系统树上，Ｂａｇａｒｉｕｓ是最原始的属，并与所有其他的物种形成姊妹群。其余８个属形成一个单系类群并分为二个姊妹群。尽管在形态上具有１３个离征，但在分子系统树上，鱼类并未形成一个单系类群。可能的原因是３３３ｂｐ序列中的星系信息位点太少；另外单从福尔马林浸制标本获得的ＤＮＡ序列的可靠性尚有待进一步验证

PRELIMINARY STUDY ON MITOCHONDRIAL CYTOCHROME b DNA SEQUENCES AND PHYLOGENY OF FORMALIN FIXED SISORID FISHES (Teleostei:Siluriformes)

bp mitochondrial cytochrome b gene fragment were sequenced from 9 sisorid species of formalin fixed tissues which represent 8 genera of family Sisoridae.Aligned under the software MUST,there are 101 various sites and 39 informative sites.Sequence pairwise distance between species ranges from 8 to 48.The mean interspecies distance ranges from 2 4% to 14 4%.Parsimony analysis generated one maximum parsimonious trees of 162 steps (CI=0 735,RI=0 494).The MP tree indicates that Bagarius is the most primitive genus,and forms a sister group with all other researched groups.The other 8 individuals form a monophyly and they can be divided into 2 sister groups.In the molecular cladogram,the glyptosternoid fishes is not monophyly although it is defined by 13 osteological apomorphies.The uncongruence of cladograms between molecular and morphological sets may be caused by less informative of 333 bp DNA sequences,or unsuitability of cytochrome b gene for phylogeny of Sisoridae.Because no fresh fish material was used,the DNA sequences only obtained from formalin fixed tissue have to be further tested,and verified.