Phylogenetic affinities of Forticulcitinae (Haploporidae) parasites of mullet from the Americas, with the description of three new species and notes on the genera and key species.

Members of Forticulcitinae Blasco-Costa, Balbuena, Kostadinova & Olson, 2009 include endoparasites of mullet fishes distributed worldwide. Adult specimens were collected from the intestines of white mullet (Mugil curema) and flathead grey mullet (Mugil cephalus) from five localities in the Gulf of Mexico and a single locality in Venezuela. Photogenophores were sequenced for two nuclear molecular markers, the large subunit (LSU) and second internal transcribed spacer (ITS2) of nuclear rDNA. The new sequences were aligned with other sequences downloaded from GenBank. The maximum likelihood and Bayesian inferences were deduced using the combined dataset (LSU + ITS2). The phylogenetic analyses revealed four new lineages belonging to Forticulcitinae. Three new species are described in the present study. Ekuarhuni mexicanus n. sp. can be differentiated from its congeneric species by presenting a longer hermaphroditic sac length (136-180 μm) and a wider testis (91-123 μm). Forticulcita macropharyngis n. sp. and Forticulcita venezuelensis n. sp. are the 8th and 9th species described in Forticulcita. Both species belong to the diminutive morphotype of Forticulcita. Forticulcita macropharyngis n. sp. can be morphologically distinguished from the other congeneric species by the presence of a massive and muscular pharynx (46-110 μm long, 74-106 μm wide). Forticulcita venezuelensis n. sp. is the second species of the studied genus recorded in South America and can be differentiated from congeneric species by possessing the largest testis (138-201 μm long, 83-100 μm wide). Finally, the fourth lineage corresponds to Overstreetoides Andrade-Gómez & García-Varela, 2021; however, few specimens of this lineage were collected, precluding any description of the species. In addition, a key is proposed for differentiating the genera and species of Forticulcitinae.