Uncovering species of the Monopisthocotyla and Polyopisthocotyla (Platyhelminthes) parasitizing Polydactylus spp. (Perciformes: Polynemidae) from the Mexican Pacific coast: two new species of Acanthocercodes (Diplectanidae) and other previously described species.

As part of a project to discover the diversity of fish parasites from Acapulco Bay on the coast of Guerrero in the Mexican Pacific, four species of the Monopisthocotyla (including two new species) and a species of the Polyopisthocotyla are described and compared with congeneric species: Octouncuhaptor sp. from the gills of the blue bobo, Polydactylus approximans (Lay & Bennett, 1839); Pseudempleurosoma sp. (Dactylogyridae) from the oesophagus of the yellow bobo Polydactylus opercularis (Gill); Acanthocercodes bullardiodes n. sp. and Acanthocercodes pacificus n. sp. (Diplectanidae) (all of the Monopisthocotyla) from the gills of P. opercularis (type host for both) and P. approximans; and Microcotyloides impudicus Caballero, Bravo & Grocott, 1955 (Polyopisthocotyla: Microcotylidae) from the gills of P. approximans. Octouncuhaptor sp. is mainly distinguished from its unique congeneric species, Octouncuhaptor eugerrei Mendoza-Franco, Roche & Torchin, 2008, on Eugerres brasilianus (Cuvier) (Gerreidae) from Panama by the morphology of the copulatory complex. Octouncuhaptor sp. represents a new species, but a specific name is not proposed for a single specimen in which the position of the structures of the internal soft organs (i.e., prostatic reservoir and seminal vesicle) are not visible, and those hard parts of the anatomy are not well defined to permit a complete description. The new diplectanids are distinguished from their congeners by the morphology and the size of the sclerotized parts of the haptor and peduncular spines. Measurements, supplementary observations, and new illustrations for Pseudempleurosoma sp. and M. impudicus are provided. The occurrence of interoceanic species of Acanthocercodes and Microcotyloides from the coasts of the Gulf of Mexico, South Atlantic Ocean (Brazil), and Mexican Pacific are briefly discussed.