Abstract: Objective　To analyze the structural and phylogenetic characteristics of the mitochondrial genome from Bulinus globosus, so as to provide a theoretical basis for classification and identification of species within the Bulinus genus, and to provide insights into understanding of Bulinus⁃schistosomes interactions and the mechanisms of parasite transmission.  Methods　       B. globosus samples were collected from the Ruya River basin in Zimbabwe. Mitochondrial DNA was extracted from B. globosus samples and the corresponding libraries were constructed for high⁃throughput sequencing on the Illumina NovaSeq 6000 platform. After raw sequencing data were subjected to quality control using the fastp software, genome assembly was performed using the A5⁃miseq and SPAdes tools, and genome annotation was conducted using the MITOS online server. Circular maps and sequence plots of the mitochondrial genome were generated using the CGView and OGDRAW software, and the protein conservation motifs and structures were analyzed using the TBtools software. Base composition and codon usage bias were analyzed and visualized using the software MEGA X and the ggplot2 package in the R software. In addition, a phylogenetic tree was created in the software MEGA X after sequence alignment with the software MAFFT 7, and visualized using the software iTOL.  Results　         The mitochondrial genome of B. globosus was a 13 730 bp double⁃stranded circular molecule, containing 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and 13 protein⁃coding genes, with a marked AT preference. The mitochondrial genome composition of B. globosus was similar to that of other species within the Bulinus genus. Phylogenetic analysis revealed that the complete mitochondrial genome sequence of B. globosus was clustered with B. truncatus, B. nasutus, and B. ugandae into the same evolutionary clade, and gene superfamily analysis showed that the metabolism⁃related proteins of B. globosus were highly conserved, notably the cytochrome c oxidase family, which showed a significant consistency.  Conclusions　This is the first whole mitochondrial genome sequencing to decode the compositional features of the mitochondrial genome of B. globosus from Zimbabwe and its evolutionary relationship within the Bulinus genus, which provides important insights for further understanding of the phylogeny and mitochondrial genome characteristics of the Bulinus genus.

Key words: Bulinus globosus, Mitochondrial genome, Genome composition, Phylogeny, Sequence analysis

摘要： 目的　分析球形小泡螺线粒体基因组结构及系统进化特征，为小泡螺属分类和鉴定奠定理论基础，进而为理解小泡螺与血吸虫的关系及寄生虫传播机制提供科学依据。方法　采集津巴布韦Ruya River流域球形小泡螺样本，提取螺类线粒体DNA并构建相应文库后在Illumina NovaSeq 6000平台上进行高通量测序。原始数据采用fastp软件进行质量控制后，采用A5⁃miseq和SPAdes软件进行基因组组装，利用在线服务器MITOS进行基因组注释。通过CGView和OGDRAW软件生成线粒体基因组圈图和排序图，使用TBtools软件分析蛋白质保守基序和结构，使用MEGA X软件和R软件ggplot2包进行碱基组成及密码子偏好性分析可视化。利用MAFFT 7软件进行序列比对后，在MEGA X软件中构建系统发育树，并使用iTOL软件绘制可视化进化树。结果　球形小泡螺线粒体基因组为13 730 bp的双链环状分子，包含2个核糖体RNA（ribosomal RNA，rRNA）基因、22个转运RNA（transfer RNA，tRNA）基因和13个蛋白质编码基因，显示出显著AT偏好性，其基因组成与其他小泡螺属相似。系统进化分析显示，球形小泡螺与截形小泡螺、纳苏小泡螺、乌干达小泡螺聚为同一进化分支；基因超家族分析显示，球形小泡螺代谢相关蛋白具有高度保守性，特别是细胞色素氧化酶家族具有显著一致性。结论　首次利用线粒体全基因组测序揭示了津巴布韦球形小泡螺线粒体基因组组成特征及其在小泡螺属中的进化关系，为进一步了解小泡螺属系统发育和线粒体基因组特性提供了重要依据。

关键词: 球形小泡螺, 线粒体基因组, 基因组组成, 系统发育, 序列分析