First report of a dactylogyrid, Paperna & Thurston, 1969 (Monogenoidea) infecting Nile tilapia, (Linnaeus, 1758) (Cichliformes: Cichlidae) in the United States, with a review of host and locality records in its invasive range and a phylogenetic analysis.

The parasites of Nile tilapia, (Linnaeus, 1758) are poorly documented in the United States despite the economic importance and global introduction of this African fish. Only one metazoan parasite ( Paperna, 1968; Gyrodactylidae) reportedly infects Nile tilapia in the United States. Examining Nile tilapia from a flow-through aquaculture system hydrologically linked to Sougahatchee Creek (Tallapoosa River, Auburn, Alabama), we observed a gill infection by Paperna & Thurston, 1969 (Dactylogyridae). This monogenoid was originally described from the gill of Mozambique tilapia, (Peters, 1852) from Lake Victoria, Uganda. Specimens of were studied for morphology and phylogenetic analyses using the and We identified our specimens as because they had the following combination of morphological features: marginal hooks shorter than dorsal anchor length; anchor roots reduced; dorsal anchor point bent; dorsal bar pyriform projections approximately half as long as dorsal bar width; penis short (<100 μm), not coiled, tubular, lacking swelling, having irregularly surfaced heel; and accessory piece straight and bifid. Our and phylogenies recovered our sequences in a clade with conspecific sequences and showed no obvious biogeographic pattern. reportedly infects 21 fishes of 11 genera and 3 families from 36 countries in Africa, Asia, North America, South America, and Europe. The study of Nile tilapia parasites, especially those exhibiting direct life cycles and low host specificity, is important because they comprise potential invasive species.