Soares Geusivam B, Adriano Edson A, Luque José L, Balbuena Juan A, Domingues Marcus V, Maia Antônio A M
Departamento de Medicina Veterinária, Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo (FZEA/USP), Rua Duque de Caxias Norte, 225, CEP 13635-900, Pirassununga, São Paulo, Brazil.
Universidade Federal de São Paulo, Instituto de Ciências Ambientais, Quimica e Farmacêuticas, Rua Professor Arthur Riedel, 275, Jardim Eldorado, CEP 09972-270, Diadema, São Paulo, Brazil; Departamento de Biologia Animal, Programa de Pós-Graduação em Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Rua Monteiro Lobato, 255, CEP 13083-862, Campinas, São Paulo, Brazil.
Parasitol Int. 2026 Feb;110:103128. doi: 10.1016/j.parint.2025.103128. Epub 2025 Jul 19.
The Cosmetocleithrum represents the most diverse group of monogenoids parasitizing Neotropical doradid catfishes. In this study, based on morphological and molecular data, we describe two new species, Cosmetocleithrum guamaensis n. sp. and Cosmetocleithrum taeniophallum n. sp., and assess their phylogenetic relationships within the Dactylogyridae using partial 28S rDNA sequences. Our analyses support the validity of these new taxa and suggest their phylogenetic affinity with Cosmetocleithrum species parasitizing auchenipterid catfishes. Additionally, we confirm the presence of Cosmetocleithrum falsunilatum and Cosmetocleithrum bulbocirrus in Megalodoras uranoscopus and Pterodoras granulosus, respectively, with C. falsunilatum exhibiting notable morphological variation across river basins, possibly influenced by environmental factors. Our phylogenetic results corroborate previous studies indicating two distinct Cosmetocleithrum lineages, one exclusively associated with doradids and another with both doradids and auchenipterids, with weak support for the genus' monophyly. Furthermore, we discuss morphological diversity within Cosmetocleithrum, highlighting significant variation in key diagnostic features, including haptoral structures, copulatory complex morphology, and vaginal opening orientation. These findings reinforce previous hypotheses suggesting that Cosmetocleithrum may not constitute a natural group and that taxonomic revisions are needed. The limited molecular data available for Cosmetocleithrum species (with only 13 out of 31 described species studied) and the disparity between the number of known doradid hosts and those surveyed for monogenoids highlight the urgent need for further integrative taxonomic and phylogenetic studies. This approach will be crucial for providing valuable insights and advancing our understanding of the complex evolutionary puzzle of one of the largest genera of monogenoids parasitizing Neotropical Siluriformes.
美饰铗钩虫是寄生于新热带区陶乐鲶科鲶鱼的单殖吸虫中种类最为多样的类群。在本研究中，基于形态学和分子数据，我们描述了两个新物种，即瓜马美饰铗钩虫（Cosmetocleithrum guamaensis n. sp.）和带阴茎美饰铗钩虫（Cosmetocleithrum taeniophallum n. sp.），并利用部分28S核糖体DNA序列评估它们在指环虫科内的系统发育关系。我们的分析支持了这些新分类单元的有效性，并表明它们与寄生于项鳍鲶科鲶鱼的美饰铗钩虫物种具有系统发育亲缘关系。此外，我们分别在巨陶乐鲶（Megalodoras uranoscopus）和粒陶乐鲶（Pterodoras granulosus）中确认了假美饰铗钩虫（Cosmetocleithrum falsunilatum）和球茎铗钩虫（Cosmetocleithrum bulbocirrus）的存在，假美饰铗钩虫在不同流域表现出显著的形态变异，可能受环境因素影响。我们的系统发育结果证实了先前的研究，即美饰铗钩虫存在两个不同的谱系，一个仅与陶乐鲶科相关，另一个与陶乐鲶科和项鳍鲶科都相关，对该属的单系性支持较弱。此外，我们讨论了美饰铗钩虫内部的形态多样性，强调了关键诊断特征的显著变异，包括附着器结构、交配复合体形态和阴道口方向。这些发现强化了先前的假设，即美饰铗钩虫可能不构成一个自然类群，需要进行分类修订。美饰铗钩虫物种可用的分子数据有限（在已描述的31个物种中仅研究了13个），已知的陶乐鲶科宿主数量与针对单殖吸虫调查的宿主数量之间存在差异，这突出了进一步开展综合分类学和系统发育研究的迫切需求。这种方法对于提供有价值的见解和推进我们对寄生于新热带区鲶形目最大单殖吸虫属之一的复杂进化谜题的理解至关重要。
