Carassius auratus complex has been believed to originate from East Eurasia and consist of diploid and triploid forms. Diploid form reproduces sexually, whereas triploid form possesses mixture modes of unisexual gynogenesis and sexual reproduction, which makes it a unique case to study evolutionary issues among vertebrates.  

Recently, a research group led by Prof. Gui Jianfang from Institute of Hydrobiology, Chinese Academy of Sciences (IHB) has made important progress on the cooperation project of genetic resource evaluation and diversity study of Carassius auratus complex between China and Russia. In this study, they identified 337 triploid individuals from 386 specimens of Carassius auratus complexsampled from 4 different sites of Xingkai Lake and Suifen River on the northeast Asia transboundary areas of Russia and China, and found that triploids were ubiquitous, whereas diploids existed only in SⅡ site of Suifen River. Triploid males were detected in all surveyed sites, and an unusually high triploid male incidence (23%) was found in the Chinese reach of Suifen River. Then, nuclear and cytoplasmic markers were used to analyze their genetic diversity and phylogenetic relationship. A total of 61 distinct tf alleles and 35 mtDNA CR haplotypes were revealed. Higher genetic diversity and divergence were confirmed in triploids than in diploids, and identical genetic background between triploid males and females was demonstrated. Moreover, evolutionary implications and roles of triploid males were suggested in population proliferation and diversity creation of the triploid form. 

The above research was a cooperation project of the Institute of Hydrobiology, Chinese Academy of Sciences (IHB) and the Institute of Marine Biology, Russian Academy of Sciences, and was supported by the National Basic Research Program of China andthe grant from Russian Foundation for Basic Research, It was conducted by Chinese and Russian researchers, and mainly performed by a PhD student Jiang fangfang, Prof. Gui Jianfang was the Corresponding Author. The result has been published online in Molecular Phylogenetics and Evolution (http://dx.doi.org/10.1016/j.ympev.2012.10.006).