Phylogenetic Relationships of Giant Salamander Species by Means of Analyzing Genomic Highly Repetitive DNA.

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A living fossil, the giant salamander (Cryptobranchid) now inhabits in Japan, China and USA and is classified into two genera (Andrias and Cryptobranchus) and three species (A.japonicus, A.davidianus and C.alleganiensis) by morphological characteristics. The classification is very difficult and even a taxonomist of Urodela can not classify sometimes. The scientific data concerning this giant salamanders are poor and are required for preservation of them.We tried to clarify the phylogenetic relationships of those three giant salamander species by means of analyzing the sequences of two genomic repetitive DNA.These are the fragments (about 120 bp) digested the genome DNA by a restriction enzyme, Hin dIII, and 5S rRNA genes (about 120 bp) with nontranscribed sparser (about 350 bp), from 8 and 7 specimens (A.j. : 5 and 4, A.d. : 2, C.a. : 1), respectively.By use of the fragments digested by Hin dIII, we clarified divergence of two genera, but failed to clarify divergence of the two species in the genus Andrias. On the other hand, by use of 5S rDNA with nontranscribed spacer, we clarified the divergence not only the two genera but also the two species In the genus Andrias. The genetic distance of 5S rDNA in these species suggests that differentiations should be happened in these three species. We clarified that all four specimens of A.japonicus examined bear a C to G transversion at a 52-base mononucleotide tract in the 5S rRNA gene. We also found 7 substitutions in 5S rRNA gene with spacer, specific to C.alleganiens is. It should be the distinct molecular characteristics of these species.We could not point out clearly the intraspecific variations according to the locality in two species. A.japonicus and A.davidianus.