| Summary: | 碩士 === 國立屏東科技大學 === 水產養殖系所 === 101 === The mitten crab group belongs to the Varunidae. Only two genera and species, Platyeriocheir formosa and Eriocheir japonica, are distributed in Taiwan. At present, population sizes of these two native species are dwindling due to habitat destruction by natural disasters and unrestricted over-harvesting. Moreover, E. sinensis was also introduced to Taiwan for short-term aquaculture which disregarded consequences of potential threatens to native species. The study attempted to distinguish morphological differences among E. japonica, E. sinensis, and P. formosa. Furthermore, molecular systematics and historical population dynamics were also analyzed using mitochondrial cytochrome oxidase subunit I (COI) gene sequences. These results can provide more-useful information for the conservation of these two native species. All E. japonica (n = 40) and P. formosa (n = 35) were collected from Lau-Mei Stream in New Taipei City, the Hou-Lung River in Miaoli County, and Jin-Luen in Taitung county. In total, 45 E. sinensis individuals were collected from an aquaculture farm in Pingtung County. Eighteen morphometric characters were measured and then analyzed using a primary component analysis, clustering, and one-way ANOVA. In addition, 20 individuals of each native species were randomly selected for sequencing and analysis of the COI gene. The results suggested that these three species have significant morphological differences and can be classified into three separate groups. The full-length COI gene is 1534 bp. The mean interspecific genetic distances were 0.150 ± 0.0061 for P. formosa vs. E. japonica, 0.150 ± 0.0027 for P. formosa vs. E. sinensis, and 0.045 ± 0.0027 for E. japonica vs. E. sinensis. In total, 86 and 84 variable sites were respectively observed within intraspecific sequences of P. formosa and E. japonica. Haplotype diversities (Hd) and mean nucleotide diversities (π) were 1 and 0.0063 ± 0.0032 for P. formosa and 1 and 0.0074 ± 0.0037 for E. japonica, respectively. Phylogenetic trees were constructed using Neighbor-joining (NJ) and Maximum parsimony (MP) methods. These trees presented significant clustering among the three species. When reference sequences from the NCBI were added to the analysis, results showed that E. japonica samples from Taiwan were more similar to E. hepuensis than to E. japonica samples from Japan. Fu’s and Tajama tests presented significantly minus values and suggested that historical population expansion had occurred for both E. japonica and P. formosa. In conclusion, P. formosa, E. japonica, and E. sinensis can clearly be distinguished by morphometric and COI sequence analyses. The scientific name of E. japonica on Taiwan should be corrected in the future.
Keywords: COI gene, interspecific genetic distance, mitten crab, morphometric, phylogenetic trees
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