We documented the diversity of helminth parasites of 25 fish species from 8 families occurring in the headwaters of the Coatzacoalcos river basin. This river flows along the border between the states of Oaxaca and Veracruz, in the region of the Isthmus of Tehuantepec, in south-eastern Mexico, and in northern Central America. We recorded 48 species, representing 44 genera and 29 helminth families. Six of the 25 fish species were examined for helminths for the first time; 60 new host records were reported. Nematodes and trematodes were the most abundant taxonomic groups. The helminth fauna from our study area consists of primarily central American species. Most species recorded from this area have also been captured from freshwater bodies between the Isthmus of Tehuantepec and the Isthmus of Panama. However, three species, including an acanthocephalan and two nematodes, are likely endemic to this area. We argue that, in contrast to the presence of larval helminths, which mostly depends on the geographical location of water bodies, adult helminths are an integral and consistent component of the regional community. Data on taxonomic composition and distribution of helminth fauna reported in this paper, contribute to a better understanding of this faunal component in northern Central America (CA). Furthermore, knowledge of helminth parasites of freshwater fish from Neotropical Mexico and CA facilitates prediction of which parasite species is likely to infect fish in a specific geographical area.

我们记录了Coatzacoalcos流域上游水域中8个科的25种鱼类的蠕虫寄生虫的多样性。这条河沿着瓦哈卡州和韦拉克鲁斯州之间的边界，Tehuantepec地峡区域，墨西哥东南部和中美洲北部边界流动。我们记录了48个物种，分别代表44个属和29个蠕虫科。首次对25种鱼类中的6种进行了蠕虫检查；报告了60个新的主机记录。线虫和吸虫是最丰富的生物分类群。我们研究区的蠕虫动物主要由中美洲物种组成。从该地区记录的大多数物种也已从Tehuantepec地峡和巴拿马地峡之间的淡水体中捕获。但是，三种 包括棘头龙和两个线虫，可能是该地区的地方病。我们认为，与幼虫蠕虫的存在（主要取决于水体的地理位置）相反，成年蠕虫是区域社区不可或缺的组成部分。本文报道的关于蠕虫动物群的分类学组成和分布的数据有助于更好地了解中美洲北部（CA）的动物群组成。此外，对来自墨西哥新热带地区的淡水鱼的蠕虫寄生虫的了解有助于预测在特定地理区域哪些寄生虫可能感染鱼类。这主要取决于水体的地理位置，成虫是区域社区不可或缺的组成部分。本文报道的关于蠕虫动物群的分类学组成和分布的数据有助于更好地了解中美洲北部（CA）的动物群组成。此外，对来自墨西哥新热带地区和加利福尼亚州的淡水鱼的蠕虫寄生虫的了解有助于预测在特定地理区域哪些寄生虫可能感染鱼类。这主要取决于水体的地理位置，成虫是区域社区不可或缺的组成部分。本文报道的关于蠕虫动物群的分类学组成和分布的数据有助于更好地了解中美洲北部（CA）的动物群组成。此外，对来自墨西哥新热带地区和加利福尼亚州的淡水鱼的蠕虫寄生虫的了解有助于预测在特定地理区域哪些寄生虫可能感染鱼类。