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In parasitic organisms, particularly helminths, the usage of the mitochondrial cytochrome c oxidase subunit I gene as the standard DNA barcoding region for species identification and discovery has been very limited. Here, we present an integrated study, based on both DNA barcoding and morphological analyses, for acanthocephalans belonging to the genus Polymorphus, whose larvae (cystacanths) are commonly found in the mesentery of freshwater fishes, while adults are found in the intestine of fish-eating birds. The alpha taxonomy of parasitic helminths is based on adult morphological traits, and because of that larval forms cannot be identified to species level based on morphology alone. DNA barcoding offers an alternative tool for linking larval stages of parasitic organisms to known adults. We sequenced cystacanths collected from freshwater fishes in localities across central Mexico and adults obtained from fish-eating birds, to determine whether they were conspecific. To corroborate the molecular results, we conducted a morphometric analysis with 'Proboscis profiler', which is a software tool developed to detect heterogeneity in morphologically similar acanthocephalans based on the multivariate statistical analysis of proboscis hook dimensions. Both sources of information indicate that cystacanths infecting freshwater fishes in central Mexico belong to a single species, Polymorphus brevis. [ABSTRACT FROM AUTHOR]

We examine the taxonomic composition and endemism of adult helminth parasites of freshwater fishes of Mexico, with regard to the main hydrological basins of the country. A presence-absence matrix, including every species of adult helminth parasites of freshwater fishes from 23 Mexican hydrological basins was compiled and examined in this paper. The helminth fauna of freshwater fishes of Mexico consists of a large group of Central American Neotropical species ( S = 119) and another set, less rich of Nearctic species ( S = 48), which are distributed along with the families of its fish hosts; insufficient data preclude the assignation of three species. This fauna is composed predominantly by nematodes, trematodes, and monogeneans, which together contributed 86 % of the total species recorded; cestodes and acanthocephalans being the taxa with the least species recorded. Current data suggests a 22 % (37/170) endemism amongst helminths of freshwater fishes of Mexico. Data suggests that the isolation of bodies of water in the Mexican territory, mostly in the Neotropical areas of southeastern Mexico and in the central Altiplano Mexicano (Mexican Highland Plateau), with well delimited basins separated by orographic features, provided peculiar conditions that have been conducive to the diversification of a unique helminth fauna. [ABSTRACT FROM AUTHOR]

In order to draw patterns in helminth parasite composition and species richness in Mexican freshwater fishes we analyse a presence-absence matrix representing every species of adult helminth parasites of freshwater fishes from 23 Mexican hydrological basins. We examine the distributional patterns of the helminth parasites with regard to the main hydrological basins of the country, and in doing so we identify areas of high diversity and point out the biotic similarities and differences among drainage basins. Our dataset allows us to evaluate the relationships among drainage basins in terms of helminth diversity. This paper shows that the helminth fauna of freshwater fishes of Mexico can characterise hydrological basins the same way as fish families do, and that the basins of south-eastern Mexico are home to a rich, predominantly Neotropical, helminth fauna whereas the basins of the Mexican Highland Plateau and the Nearctic area of Mexico harbour a less diverse Nearctic fauna, following the same pattern of distribution of their fish host families. The composition of the helminth fauna of each particular basin depends on the structure of the fish community rather than on the limnological characteristics and geographical position of the basin itself. This work shows distance decay of similarity and a clear linkage between host and parasite distributions. [ABSTRACT FROM AUTHOR]

n inventory based on previously published records and original data is presented for the helminth parasites reported in 54 fish species from 17 families from the state of Chiapas, southeast Mexico. This survey reports the presence of 43 helminth species in Chiapas for the first time. The actualized inventory of helminth parasites of freshwater fish from Chiapas contains 88 species from 67 genera and 40 helminth families. Trematodes and nematodes were the most abundant taxonomic groups. The helminth fauna in freshwater fishes from Chiapas consists of Central American species. All the helminth species recorded in Chiapas have also been collected from bodies of freshwater between the Isthmus of Tehuantepec and the Isthmus of Panama. This inventory shows that this fauna is quite similar to that from the neighboring basins of the lower Grijalva-Usumacinta system and the Yucatan Peninsula. The taxonomic composition and distribution data reported here for the helminth fauna of Chiapas' freshwater fish, contribute to a better understanding of this faunal component in Central America. [ABSTRACT FROM AUTHOR]

The distributional patterns of helminthological fauna of freshwater fishes were analysed to postulate a general hypothesis on the relationships of some Mexican hydrological systems. Eight hydrological systems of central and eastern Mexico were studied and compared with records from Nicaragua. A Parsimony Analysis of Endemicity (PAE) was applied to the presence/absence of ninety-two helminth parasite taxa (Monogeneans, Digeneans, Cestodes, Acanthocephalans and Nematodes) of freshwater fishes, from eight Mexican hydrological systems, using the Hennig86 program. The results represent the first attempt for a biogeographical analysis through application of the PAE method to the distributional patterns of helminth parasites of freshwater fishes in Mexico. A single most parsimonious cladogram was obtained, which grouped all the Neotropical systems in accordance with previous proposals based on other plant and animal taxa. The most basal systems were Santiago and Lerma basins, which exhibited Nearctic affinities. The remaining areas of the cladogram showed Neotropical affinities. All the southeastern systems were grouped in a clade with the Nicaragua system, providing support for a ‘Mesoamerican province’ based on helminth parasites of cichlids. The cladogram also suggests that the treatment of the Lerma-Santiago basin as a single biogeographical unit is inaccurate and that they should be treated as separate systems. [ABSTRACT FROM AUTHOR]