Molecular characterization of two <i>Myxidium</i> species (Cnidaria: Bivalvulida: Myxidiidae) infecting barbs in the Sea of Galilee, Israel

Myxozoans are parasitic cnidarians that can cause severe damage to fish, resulting in economic losses to aquaculture and fisheries. In Israel, only a few taxonomic studies have been conducted on Myxozoa infecting freshwater fish and none on barb parasites. Here, we describe two new myxozoan species - <i>Myxidium grauri</i> n. sp. and <i>Myxidium sharmai</i> n. sp. - from the gallbladder of the barbs <i>Carasobarbus canis</i> and <i>Luciobarbus longiceps</i>, respectively, from the Sea of Galilee (Lake Kinneret). The prevalence of infection was 42.2% (19/45) for <i>M. grauri</i> n. sp. and 25% (5/20) for <i>M. sharmai</i> n. sp. We obtained 18S rRNA sequences for both species, providing the first molecular data on <i>Myxidium</i> infecting barbs from the Sea of Galilee. Phylogenetic analysis confirmed that the genera <i>Myxidium</i> and <i>Zschokkella</i> are not monophyletic. The <i>δ</i>-statistic was used to assess the phylogenetic signal of categorical traits within the Biliary Tract Clade IV lineage, which includes the species studied. The analysis revealed a significant phylogenetic signal associated with the host clade, the parasite's geographic origin and the type of environment it inhabits. However, some of these statistical results may be influenced by sampling bias, as Percomorpha and Otomorpha fish are disproportionately represented in marine and freshwater environments, respectively. The newly obtained sequences form a distinct lineage within a clade of freshwater-infecting myxozoans. Our findings suggest that myxozoan infections are widespread in the Sea of Galilee. Given their potential impact on fisheries and the lake's ecosystem, further research is needed to assess their distribution, dynamics and ecological consequences.