长江中下游两种尖毛虫的形态学与分子系统发育研究

MORPHOLOGICAL AND MOLECULAR PHYLOGENETIC STUDY OF TWO OXYTRICHID CILIATES FROM THE MIDDLE AND LOWER REACHES OF THE YANGTZE RIVER

  • 摘要: 本研究综合利用活体观察、蛋白银染色和核糖体小亚基DNA (SSU rDNA)序列分析等方法, 对采自武汉东湖和荆州洪湖养殖鱼塘的两种腹毛类纤毛虫, 印度原毛虫Architricha indica Gupta et al., 2006和原始厚膜虫Crassohymena primicirrata (Berger & Foissner, 1987) Omar et al., 2025, 进行了形态学及系统学研究。其中原始厚膜虫为中国新记录种, 印度原毛虫为华中地区新记录种。本研究新采集的印度原毛虫武汉种群与已报道的印度原始种群及上海种群在活体形态、皮层颗粒特征、额–腹–横棘毛模式、缘棘毛数目(3列右缘和2列左缘)和背触毛模式(4列背触毛和2列背缘触毛)上高度一致。但武汉种群表现出更广的形态变异范围: 口后腹棘毛数目(1—5 vs. 3); 横棘毛数目(4—6 vs. 5)。此外, 武汉种群体型较大(150—180) μm × (50—80) μm vs. 印度种群140 μm, 上海种群(100—140) µm × (30—40) μm。尽管存在这些差异, 但三个种群的关键特征参数范围存在重叠, 应视为种内差异。原始厚膜虫的洪湖种群在第4列背触毛长度和小核数目等特征上与奥地利种群一致, 但是与韩国种群存在一定差异, 补充了该物种在不同地理分布区间的形态多样性信息。分子系统学结果进一步支持了这两个种的分类鉴定: 印度原毛虫武汉种群与上海种群的SSU rDNA序列相似度为99.76%, 仅有4个碱基差异, 两者在系统发育树中稳定地聚在一起; 原始厚膜虫洪湖种群与两个韩国种群的SSU rDNA序列完全一致, 三者在系统发育树中稳定地聚为一支。通过形态学重描述和分子序列分析, 丰富了尖毛虫科Oxytrichidae Ehrenberg, 1830的系统分类信息, 同时为认识长江中下游淡水湿地纤毛虫的区域分布格局和多样性提供了新的证据。

     

    Abstract: In the present study, we investigated two hypotrichous ciliates, Architricha indica Gupta et al., 2006, collected from Donghu Lake in Wuhan, and Crassohymena primicirrata (Berger & Foissner, 1987) Omar et al., 2025, obtained from an aquaculture pond in Honghu, Jingzhou. Morphological analyses based on live observation and protargol staining were combined with small-subunit ribosomal DNA (SSU rDNA) sequencing and phylogenetic reconstruction. Our results show that C. primicirrata is recorded for the first time in China, whereas A. indica represents a new record for central China. The Wuhan population of A. indica was consistent with the Indian and Shanghai populations in living morphology, cortical granules, frontal-ventral-transverse cirral pattern, number of marginal cirri (three right and two left rows), and the dorsal ciliature (four dorsal and two dorsomarginal rows). Nevertheless, the Wuhan population exhibits a broader morphometric range in the number of postoral ventral cirri (1—5 vs. 3) and transverse cirri (4—6 vs. 5), with larger body size (150—180) μm× (50—80) μm vs. 140 μm in the Indian population and (100—140) μm× (30—40) μm in the Shanghai population. Despite these differences, the overlapping diagnostic characteristics support their interpretation as intraspecific variation. The Honghu population of C. primicirrata closely resembled the Austrian population in features such as the length of the fourth dorsal kinety and the number of micronuclei, but differs in certain respects from the Korean populations, thereby enriching the knowledge of the morphological diversity across different geographic regions. Molecular phylogenetic analyses further support the species identifications. The SSU rDNA sequences of the Wuhan and Shanghai populations of A. indica show 99.76% similarity, differing by only four nucleotides, and consistently cluster together in the phylogenetic trees. The Honghu and Korean populations share identical sequences and consistently form a well-supported clade in the phylogenetic tree. By integrating morphological redescriptions with molecular data, this study contributes to the taxonomy of the family Oxytrichidae, and provides new insights into the biodiversity and biogeography of ciliates in the middle and lower reaches of the Yangtze River.

     

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