First record of Prosogonotrema bilabiatum Vigueras, 1940 (digenea: Sclerodistomidae) in marine fishes from the Persian Gulf, Hormozgan Province, Southern Iran.

BACKGROUND: This study documents the first occurrence of the digenean trematode Prosogonotrema bilabiatum in marine fish from the Persian Gulf, Iran. METHODS: One hundred eighty-two specimens of four ecologically and economically important marine fish species (Alectis indica, Rachycentron canadum, Seriola dumerili, and Solea elongata) were examined between January 2023 and December 2024 in Hormozgan Province using light microscopy and molecular techniques. RESULTS: Among the sampled fish, the overall prevalence of P. bilabiatum was found to be 31.31% (57/182). Molecular analyses targeting the nuclear 28 S rRNA and mitochondrial cytochrome c oxidase subunit I (COI) genes corroborated the morphological identification of P. bilabiatum. Phylogenetic reconstruction based on 28 S sequences clustered the Iranian isolates with Brazilian P. bilabiatum with strong nodal support, confirming their taxonomic placement within Sclerodistomidae. In contrast, COI analyses placed the Iranian isolates in a distinct monophyletic clade, but no reference COI sequences of Prosogonotrema genus were available in GenBank for direct comparison. Accordingly, the present study provides the first COI sequences for the genus, establishing a novel molecular reference for future phylogenetic studies. CONCLUSION: Our finding underscores the importance of integrative taxonomy in documenting parasite diversity in understudied marine ecosystems such as the Persian Gulf, where climate-related environmental changes may alter parasite distributions. Continued parasitological monitoring, complemented by molecular and phylogenetic approaches, will be essential for clarifying species boundaries within genus Prosogonotrema and for assessing the ecological and fisheries implications of trematode infections in the region.