New species of Neodiplostomum (Trematoda: Diplostomidae) from Argentine Patagonian birds: morphological and molecular characterisation

This study describes two new species of Neodiplostomum (Trematoda: Diplostomidae) and reports a new lineage parasitising birds in Northwestern Patagonia, Argentina, based on morphological and molecular evidence. Specimens were recovered from the intestines of Falco sparverius, Caracara plancus, Accipiter bicolor, and Strix rufipes between 2001 and 2025. Morphological analyses revealed that the new taxa, herein named Neodiplostomum sparverius n. sp., and Neodiplostomum caracara n. sp., and the unnamed species Neodiplostomum sp. 1 show differences mainly in body segment ratio, sucker size, and vitelline gland distribution. This work contributes 14 new sequences to this genus. Phylogenetic analyses of nuclear (28S rDNA) and mitochondrial (cox1) sequences placed N. sparverius n. sp. within a clade comprising Neodiplostomum banghami and Neodiplostomum americanum; Neodiplostomum sp. 1 clustered with Neodiplostomum microcotyle and Neodiplostomum vaucheri, among others, confirming the existence of two well-supported Neodiplostomum lineages: the first is restricted to avian hosts, whereas the second includes birds and mammals. These results provide the first record of species of the genus Neodiplostomum in Patagonia, and the first molecular sequences for species of this genus in Argentina, thus expanding the known diversity and distribution of the genus in South America. The integrative approach supports the need for taxonomic revision of the genus Neodiplostomum.