Blood flukes (Digenea: Sanguinicolidae) of common freshwater fishes in Europe: A new genus, two new species, and a morphological and molecular characterisation of Sanguinicola armatus

Fish blood flukes are important parasites that can cause mortalities of their hosts. Yet, blood flukes of freshwater fishes are understudied worldwide. Herein, we provide new information on the family Sanguinicolidae using specimens from freshwater fishes in Lithuania. The sanguinicolids were identified using molecular (nuclear 28S rDNA and mitochondrial cox 1 DNA) and morphological data. Within the type-genus Sanguinicola , we provide the first genetic characterisation of the type-species Sanguinicola armatus using newly obtained specimens from the type-host Tinca tinca (Tincidae), report new host and geographical records for Sanguinicola volgensis , and describe a new species Sanguinicola bakeri n. sp. from Blicca bjoerkna (Leuciscidae). Sanguinicola bakeri n. sp. is distinguished from congeneric species by the possession of small lateral testicular lobes, an elongate ovary (occupying 16–18% of body length) and a narrow oviducal seminal receptacle. Phylogenetic analysis based on 28S rDNA sequences confirmed the distinct status of S . bakeri n. sp. within the genus Sanguinicola . We propose a new genus, Ejsmontellus n. g., comprising Ejsmontellus akicola n. sp. (type-species) infecting B . bjoerkna and unidentified Ejsmontellus sp. from Leuciscus leuciscus (Leuciscidae). Ejsmontellus n. g. is diagnosed by the possession of single columns of ventrolateral tegumental spines, a tubular swelling at the anterior end of the oesophagus, a compact heart-shaped ovary, and the lack of posterior oesophageal swelling. Phylogenetically, Ejsmontellus n. g. is distant from Sanguinicola and closest to a clade comprising cercarial isolates from pulmonate snails from Czechia, Poland and South Africa. The discovery of new sanguinicolids from commonly occurring fishes and availability of DNA sequences of undescribed species show that fish blood flukes remain underexplored.