Molecular phylogeny of Kritsky, Thatcher & Boeger, 1986 (Monogenoidea: Dactylogyridae), gill parasites of Neotropical catfishes (Siluriformes).

Kritsky, Thatcher & Boeger, 1986 (Dactylogyridae) represents one of the most species-rich groups (22 species currently recognized as valid) of all dactylogyrid parasites infecting Neotropical catfishes. Species of exhibit a remarkable affinity towards catfishes of the Doradidae and the Auchenipteridae. However, phylogenetic relationships between members of this genus have not been yet analysed. This study analysed newly obtained partial sequences of the 28S ribosomal RNA gene of seven species of , including its type species . Kritsky, Thatcher & Boeger, 1986, along with several other dactylogyrids infecting siluriform, gymnotiform, perciform and characiform fishes. appeared as an evolutionary recent group, composed of two well-defined lineages: lineage 1 includes parasites of doradids - namely, . , . , . and . - whereas lineage 2 is composed of species from doradids - that is, . , . , . , . and . - together with parasites of auchenipterids - namely, . and . . The search for synapomorphies to characterize taxonomic groups within appears challenging, since the morphology of their haptoral elements is quite conservative, and that of the copulatory complex is highly variable between species. The results of the present study support the recent synonymization of Acosta, Scholz, Blasco-Costa, Alves & Silva, 2018 with . Whereas the 28S ribosomal DNA data resolved as monophyletic, the statistical support for the lineage was low, rendering its phylogenetic position between other Neotropical dactylogyrids yet undefined.