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Abstract：
The use of molecular tools in the study of parasite taxonomy and systematics have become a substantial and crucial component of parasitology. Having genetic characterisation at the disposal of researchers has produced mostly useful, and arguably more objective conclusions. However, there are several groups for which limited genetic information is available and, coupled with the lack of standardised protocols, renders molecular study of these groups challenging. The Diplozoidae are fascinating and unique monogeneans parasitizing mainly freshwater cyprinid fishes in Europe, Asia and Africa. This group was studied from a molecular aspect since the turn of the century and as such, limitations and variability concerning the use of these techniques have not been clearly defined. In this review, all literature and molecular information, primarily from online databases such as GenBank, were compiled and scrupulously analysed for the Diplozoidae. This was done to review the information, detect possible pitfalls, and provide a \"checkpoint\" for future molecular studies of the family. Hindrances detected are the availability of sequence data for only a limited number of species, frequently limited to a single sequence per species, and the heavy reliance on one non-coding ribosomal marker (ITS2 rDNA) which is difficult to align objectively and displays massive divergences between taxa. Challenging species identification and limited understanding of diplozoid species diversity and plasticity are also likely restricting factors, all of which hamper the accurate taxonomic and phylogenetic study of this group. Thus, a more integrated taxonomic approach through the inclusion of additional markers, application of more rigorous morphological assessment, more structured barcoding techniques, alongside thorough capturing of species descriptions including genetypes, genophore vouchers and reference collections in open sources are encouraged. The pitfalls highlighted are not singular to the Diplozoidae, and the study of other groups may benefit from the points raised here as well.
摘要：
在寄生虫分类学和系统学研究中使用分子工具已成为寄生虫学的重要组成部分。由研究人员支配的遗传表征产生了大多数有用的，可以说是更客观的结论。然而,有几个群体的遗传信息有限，再加上缺乏标准化的协议，使得这些群体的分子研究具有挑战性。二倍体科是迷人且独特的单系动物，主要寄生在欧洲的淡水鲤科鱼类，亚洲和非洲。自世纪之交以来，该小组从分子方面进行了研究，因此，关于使用这些技术的局限性和可变性尚未明确定义。在这次审查中,所有文献和分子信息，主要来自GenBank等在线数据库，对二倍体科进行了汇编和仔细分析。这样做是为了审查信息，检测可能的陷阱，并为该家族的未来分子研究提供一个“检查点”。检测到的阻碍是只有有限数量的物种的序列数据的可用性，通常限于每个物种的单个序列，以及对一个非编码核糖体标记（ITS2rDNA）的严重依赖，该标记很难客观地对齐，并且在分类单元之间显示出巨大的差异。具有挑战性的物种鉴定和对二倍体物种多样性和可塑性的有限理解也可能是制约因素。所有这些都阻碍了该群体的准确分类和系统发育研究。因此，一种更综合的分类学方法，通过包含额外的标记，应用更严格的形态学评估，更结构化的条形码技术，除了彻底捕获物种描述，包括基因型，鼓励开放来源的基因细胞凭证和参考收藏。突出显示的陷阱并不是二倍体科所独有的，其他群体的研究也可能受益于这里提出的观点。
