Preliminary Study on Mitochondrial Cytochrome b DNA Sequences and Phylogeny of Formalin Fixed Sisorid Fishes

333 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 usd,the DNA sequences only obtained from formalin fixed tissue have to be further tested,and verified.