CHARACTERISTICS OF LINEAGE, PLOIDY AND SEX OF CORBICULA CLAMS FROM THE YUAN RIVER IN CHANGDE CITY

Due to the extraordinary range of morphological change and plasticity, coexistence of synonyms in genus Corbicula has been proposed. Meanwhile, diversified reproductive modes and polyploidies furtherly complexed the classification of genus Corbicula, which should be solved using more comprehensive and integrated methods. In order to deduce the systematic classification and study the reproductive mode of genus Corbicula clams, the lineages of genus Corbicula clams in the Changde City section of Yuan River was constructed based on mitochondrial COⅠ maker, and the relationships, morphology, ploidy, sex and genetic diversity in this study were analyzed. The results showed that 17 variation sites in 12 COⅠ haplotypes were detected in 99 COⅠ sequences (526 bp), and the haplotype diversity, nucleotide diversity, and mean nucleotide variation were 0.599, 0.01236 and 6.503, respectively. All Corbicula clams were classified into two separate clades based on the phylogenetic tree, respectively, corresponding to the previously reported lineage RA and RlcB, but the shell length, shell height, and shell width were not different significantly between lineages (P>0.05). Of 99 specimens analyzed, there were 50 diploids, 49 triploids, 71 hermaphrodites, 21 females, and 7 males. Chi-square tests detected significant relationships between lineage and sex (P=0.004) and between ploidy and sex (P=0.005). The number of haplotypes, total number of variable sites, nucleotide diversity, and mean number of nucleotide variation of lineage RlcB were higher than those of lineage RA. All above results showed that RA and RlcB have some differences in morphology, ploidy, sex, and genetic diversity, but all these biological characteristics were not enough to discriminate Corbicula clams from other lineages, and more directed and robust evidences should be used to further confirm that lineage RA and RlcB belong to two different species.