Remarks on the diversity of Hysteromorpha Lutz 1931 (Digenea, Diplostomidae), with erection of a new species from South America

Abstract

Hysteromorpha Lutz, 1931 is a small but broadly distributed genus of diplostomoidean digeneansparasitic as adults primarily in cormorants, but also reported from some other fish-eating birds. Theirmetacercariae were found in a variety of freshwater fishes as second intermediate hosts. Prior to thisstudy, the genus included only 3 nominal species, 2 of them distributed in the Old World and 1 in theNew World. We obtained sequences of partial mitochondrial cox1 gene and nuclear rDNA operon fromnew specimens collected in Europe, North and South America and used them for species comparisonsand phylogenetic analysis. We also examined morphology of our newly collected specimens as well asmuseum specimens. Our analysis has demonstrated that at least 2 (likely 3) species of Hysteromorphaare distributed in the Americas. Hysteromorpha sp. previously sequenced by López-Hernández et al.(2019) from larval stages, clearly represents a new species named herein as Hysteromorphaostrowskiae n. sp. Achatz, Locke et Tkach. Morphology of adults of the new species was described byOstrowski de Nuñez (1970) under the name Hysteromorpha triloba (Rudolphi, 1819). Our analysesalso suggest the presence of another unknown Hysteromorpha sp. in North America represented bycox1 sequence from southeastern Canada (GenBank JF769473), but no morphological vouchers areavailable for this species.