Integrative analysis of newmetacercariae (Digenea, Clinostomidae) using COI mtDNA and morphology rises the number of lineages found in South American freshwater fishes.

Abstract

Clinostomidae is a diverse family of digenean parasitizing fish-eating birds as adults and fishes as metacercariae. The species composition, within the genushas been steadily increasing in recent years. In Argentina, four named species ofhave been documented, accompanied by four metacercariae representing distinct genetic lineages whose adults have not been identified. This study focused on examining clinostomids in three fish species -(ASI),(CDIM), and(PLA) - at various localities in Argentina. We conducted both morphological and molecular characterizations of themetacercariae collected from these fish species. Molecular phylogenetic analyses using COI mtDNA were performed to determine the placement of these metacercariae within the clinostomid phylogenetic tree.ASC represents a distinct lineage, morphologically distinguishable from other sequenced metacercariae due to its body shape (widest anteriorly and becoming slender towards the posterior end); this lineage was found to be closely related toWhileCDIM andPLA exhibited morphological differences, they clustered together genetically with metacercariae reported in previous studies asL3 andCVI. This outcome, coupled with a low genetic distance (0 to 3%), suggests that they are conspecific with metacercariae found in fish across Mexico, Costa Rica, and Argentina. In light of the extensive diversity of fish species in Argentine freshwater ecosystems (over 500 species), and considering the relatively constrained extent of prior investigations, the anticipation of unearthing additionalspecies or lineages is plausible.