Neotropical sisterhood: new species of von Nordmann, 1832 (Platyhelminthes: Monogenea) infecting and (Siluriformes: Heptapteridae) in Mexico.

We describe two new species of monogenean parasites of the genus von Nordmann, 1832 infecting Neotropical catfishes (Siluriformes) in southern Mexico: n. sp. from 'chulín', collected in Oaxaca; and n. sp. from 'juil', from Veracruz. Morphologically, both new taxa are similar to spp. infecting catfishes (Siluriformes) in South America. Sequences of the internal transcribed spacers (ITS1-5.8S-ITS2 rDNA), the D2+D3 domains of the large ribosomal subunit (28S rDNA) and the cytochrome oxidase II (COII) gene were obtained from multiple parasite specimens and analysed using Bayesian inference. Phylogenetic hypotheses using ITS rDNA and COII genes, recovered two new species from spp.: n. sp.; and n. sp., which are sister species to , a parasite of in Brazil, and show strong affinity to other gyrodactytlids infecting Neotropical catfishes. This suggests that these new taxa, the first gyrodactylids described from spp. in Mexico, co-migrated to Tropical Middle America with their Neotropical catfish hosts, after the emergence of the Isthmus of Panama.