Taxonomic And Phylogenetic Studies Of The Saccostrea Oysters On The Coastal Areas Of China

Oysters have high morphological plasticity and are easy to change their shell characteristics with the environment.The traditional classification mainly based on shell morphology and anatomical structure,which can lead to the confusions on oyster classification.Saccostrea oysters restrictly distribut to tropical and subtropical waters.Saccostrea is the most common and most abundant oyster in the southern coastal zone of China,most species are attached to exposed rocks or coral reefs.The shell morphology of Saccostrea species are similarity,so the classification on Saccostrea oyster is more controversial.Based on traditional morphological classification,this study analysed the classification of genus Saccostrea using mitochondrial genes of cytochrome oxidase I(COI)and 16 SrRNA and nuclear gene 28 SrRNA calrified the distribution of Saccostrea from coastal intertidal zone of China.In present study,we collected 1773 oysters of Saccostrea,and identified seven species including two new species and two new records of Chinese waters.S.mordoidea sp.nov.and S.kegakioidea sp.nov.are two new species.The two new records include S.malabonensis and S.circumsuta.The remaining three oysters are common oysters on China's coastal intertidal.They are S.mordax,S.kegaki and S.echinata.Currently,S.mordoidea sp.nov.is distributed in Haitang bay in Hainan Province.S.kegakioidea sp.nov.is found only in Nanji Islands and Shengsi Islands of Zhejiang Province.S.malabonensis is abundant,and mainly distributes in Guangdong and Hainan coastal intertidal.There are a few individuals of S.circumsuta,distributed in Guangdong,Hong Kong,Guangxi and Hainan coastal intertidal.S.mordax is distributed in Yangjiang Guangdong Province and Hainan coastal intertidal,where S.kegaki is found on exposed rocks in Nanji Islands,Shengsi Islands,Zhejiang coastal intertidal and Dongchong Peninsula.S.echinata is the largest and most widely spread oysters,distributed in Zhejiang,Fujian,Guangdong,Guangxi and Hainan coastal intertidal.This research clarified the classification confusion of genus Saccostrea along China's coastal intertidal,and determined their distribution.According the phylogenetic tree of the genus Saccostrea established using the mitochondrial gene(16SrRNA and COI)and nuclear gene(28SrRNA),the interspecies relationship of genus Saccostrea oyster was determined.This study provides the basic information for biodiversity investigation conservation,ecological research and aquaculture.