Division of Cell Biology, Department of Preclinical Sciences, Faculty of Medicine, Thammasat University, Rangsit Campus, Pathumthani 12120, Thailand.
Walai Rukhavej Botanical Research Institute, Biodiversity and Conservation Research Unit, Mahasarakham University, Maha Sarakham 44150, Thailand.
Int J Parasitol. 2020 Jan;50(1):55-62. doi: 10.1016/j.ijpara.2019.10.007. Epub 2019 Dec 18.
The freshwater snail Bithynia siamensis goniomphalos sensu lato is widely distributed in the Lower Mekong Basin where it acts as the first intermediate host of the liver fluke Opisthorchis viverrini, a group 1 carcinogen causing cholangiocarcinoma. This study explores the genetic structure and geographical variation of B. s. goniomphalos from eight previously studied catchments and eight new catchments. These catchments belong to five previously studied catchment systems and one new catchment system (Tonlesap) in the Lower Mekong Basin. Two new catchment systems, Prachin Buri and Bang Pakong from eastern and central Thailand, respectively, were also examined. We collected 289 specimens of B. s. goniomphalos from 15 previously studied localities and 18 new localities in Thailand, Lao PDR (People's Democratic Republic), and Cambodia. The mitochondrial cytochrome c oxidase subunit 1 and 16S ribosomal DNA sequences were used to determine genetic variation. Classification of haplotypes specified 100 at the cox1 locus and 15 at the rrnL locus. Comparison between 16 catchment populations found significant genetic differences (Ф) between all populations. The phylogenetic tree and haplotype network analyses classified B. s. goniomphalos into three evolutionary lineages (lineage I-III). Lineage I contained B. s. goniomphalos from the Mekong, Chi, Mun, Prachin Buri and Bang Pakong catchments in Thailand, including the Nam Ngum catchment in Lao PDR. Lineage II contained all specimens from the Tonlesap catchment, whereas lineage III contained specimens from the Mekong and Sea Bang Heang catchments in Thailand and Lao PDR, respectively. Interestingly, Bithynia siamensis siamensis was placed between lineages I and II of B. s. goniomphalos. This study supports the hypothesis that B. s. goniomphalos is a species complex containing at least three distinct evolutionary lineages in the Lower Mekong Basin, and that comprehensive molecular genetic analyses need to be conducted to further our understanding of the evolutionary and systematic relationships of these Bithynia snail taxa.
宽体蜷贝（Bithynia siamensis goniomphalos sensu lato）广泛分布于湄公河流域下游，是肝吸虫（Opisthorchis viverrini）的第一中间宿主，肝吸虫被国际癌症研究机构列为 1 类致癌物，可导致胆管癌。本研究探索了湄公河流域下游 8 个已有研究集水区和 8 个新集水区的宽体蜷贝（Bithynia siamensis goniomphalos sensu lato）的遗传结构和地理变异。这些集水区属于湄公河流域下游五个已有研究集水系统和一个新集水系统（Tonlesap）。此外，还研究了来自泰国东部和中部 Prachin Buri 和 Bang Pakong 的两个新集水系统。我们从泰国、老挝人民民主共和国和柬埔寨的 15 个已有研究地点和 18 个新地点收集了 289 只宽体蜷贝（Bithynia siamensis goniomphalos sensu lato）标本。使用线粒体细胞色素 c 氧化酶亚基 1 和 16S 核糖体 DNA 序列来确定遗传变异。在 cox1 基因座上指定了 100 个单倍型，在 rrnL 基因座上指定了 15 个单倍型。对 16 个集水区种群的比较发现，所有种群之间存在显著的遗传差异（Ф）。系统发生树和单倍型网络分析将宽体蜷贝（Bithynia siamensis goniomphalos sensu lato）分为三个进化谱系（谱系 I-III）。谱系 I 包含来自湄公河、赤陶、芒、Prachin Buri 和 Bang Pakong 集水区的宽体蜷贝（Bithynia siamensis goniomphalos sensu lato），包括老挝人民民主共和国的 Nam Ngum 集水区。谱系 II 包含来自 Tonlesap 集水区的所有标本，而谱系 III 包含来自泰国和老挝人民民主共和国的湄公河和 Sea Bang Heang 集水区的标本。有趣的是，暹罗蜷贝（Bithynia siamensis siamensis）位于宽体蜷贝（Bithynia siamensis goniomphalos sensu lato）的谱系 I 和 II 之间。本研究支持宽体蜷贝（Bithynia siamensis goniomphalos sensu lato）是一个物种复合体的假说，该复合体在湄公河流域下游至少包含三个不同的进化谱系，需要进行全面的分子遗传分析，以进一步了解这些暹罗贝螺类的进化和系统关系。
