A new species of <scp><i>Kannaphallus</i></scp> (Polyopisthocotylea: Heteraxinidae) parasitic on the twobar seabream <scp><i>Acanthopagrus bifasciatus</i></scp> (Sparidae, Teleostei) in Saudi Arabia

Abstract Monogeneans are highly host‐specific parasites infecting marine and freshwater fish. However, little information is available about the parasitic taxa within Heteraxinidae. An integrative study was performed to understand the taxonomic status of an unconfirmed heteraxinid marine species parasitizing the gill region of Acanthopagrus bifasciatus (Sparidae) from the Arabian Gulf (Saudi Arabia). Based on the morphological study, this parasite has all the generic features of the genus Kannaphallus (Heteraxinidae, Mazocraeidea). Distinct criteria that discriminated this species from other taxa of the same genus are the presence of genital spines (26–29), a short sclerotized duct in the male copulatory organ, the number of testes (mean 40, range 30–50), and clamps in the haptoral structure (45–50 in a long row and 19–22 in a short row). DNA of parasite species reported in the present study was amplified and sequenced for the nuclear large subunit of the ribosomal RNA ( 28S rRNA) gene and the mitochondrial cytochrome c oxidase subunit I ( COI ) gene. Results indicate that sequences obtained from both genes are unique and different from related sequences from the genus Kannaphallus . Morphological as well as molecular data indicate that our specimens are from a new species, and the name Kannaphallus acanthopagrusi n. sp. is suggested. This is the first report of a heteraxinid parasitizing marine sparid fish from Saudi Arabia, with unique morphological and molecular features.