Species Composition And Genetic Diversity Of Chitons(Polyplacophora) Along China’s Coasts

The chiton belonging to Mollusc,Polyplacophora,is kind of bilaterally symmetrical marine invertebrates with eight valves in their dorsum,and they have great values in both economical and science.The distribution range of chiton is extensive,we can find it in the oceans all the worlds.According to the previous reports,the diversity of species values of chiton was high in China,we made a field research about the status of the chiton species composition combined with the ecology investigation methods,but our research showed different results compared with the previous results,we found that the status of the chiton species composition was single,and the reason of which may due to the serious seawater pollution,or the habitat loss of chiton due to the human activity expanded.By the research we realized that the Acanthochiton rubrolineatus had the largest distribution range along China’s coasts ai the present stage,the A.rubrolineatus belonging to Cryptoplacidae,Neoloricata,Polyplacophora,the mainly distribution range along seacoasts of China,Korean Peninsula and Japan.In our research,we collected 238 A.rubrolineatus samples from eight locations of China’s coasts(Dalian,Yantai,Weihai,Qingdao,Lianyungang,Zhoushan,Yuhuan,Xiamen),combined with the mitochondrial COI and 16S-rRNA gene sequences,and the nuclear 28S-rRNA gene sequences to analyze the genetic diversity and population structure.The results based on the combined COI and 16S-rRNA gene sequences showed that there was evident genetic differentiation between the northern populations(YT,WH,DL,QD,LYG)and southern populations(ZS,YH,XM)of A.rubrolineatus.The haplotype distribution pattern and genetic diversity based on 28S-rRNA sequences also supported the genetic divergence between two groups.Both groups had experienced population expansion after the ice age of Pleistocene,and additional population bottleneck had happed in southern group in recent history,which led to low genetic diversity of mitochondrial DNA and abnormal high diversity of nuclear DNA in this group.Our results suggested that the protection on A.rubrolineatus is necessary,and the northern and southern group should be protected separately.