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

大鲵（Cryptobranchid）是一种活化石，现栖息于日本、中国和美国，根据形态特征分为2属（Andrias和Cryptobranchus）和3种（A.davidianus和C.alleganiensis）。分类是非常困难的，即使是分类学家的泌尿系统有时不能分类。目前关于大鲵的科学资料很少，为了保护大鲵，我们试图通过分析两个基因组重复DNA序列来阐明这三种大鲵的系统发育关系。（约120 bp）通过限制性内切酶、Hin dIII和5S rRNA基因消化基因组DNA（约120 bp），非转录片段（约350 bp），分别来自8和7个标本（A.j.：5和4，A.d.：2，C.a.利用Hin dIII消化的片段，我们澄清了两属的分歧，但未能澄清Andrias属中两种的分歧。另一方面，利用5SrDNA的非转录间隔区，我们不仅澄清了两属，而且澄清了两种在Andrias属中的分歧。5SrDNA的遗传距离表明，这3个种之间可能发生了分化。我们澄清，所有四个样本的A. Escherichia coli检查轴承在5S rRNA基因的52个碱基的单核苷酸序列的C到G颠换。在5SrRNA基因中还发现了7个带有间隔区的替换，这是直链梭菌特有的。这应该是这两个种的分子特征不同，我们不能清楚地指出两个种的种内变异是否因地理位置而异。A. davidianus.

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.