Parasitoid chytridiomycete Ericiomyces syringoforeus gen. et sp. nov. has unique cellular structures to infect the host

Many fungi have been identified as pathogens of marine algae. Among them, Chytridiomycota revealed relatively highly abundant, but much the diversity known within these groups is almost entirely based on environmental sequencing data. Here, we present a novel chytridiomycete genus and species, characterized by light microscopical observations, ultrastructure, molecular phylogenetic analysis parasitic chytrid brackish-water dinoflagellate Kryptoperidinium foliaceum from Baltic Sea. Phylogenetic rDNA sequences ultrastructure strain reveals that it represents new family in order Rhizophydiales. Ericiomyces syringoforeus gen. et sp. nov. parasitoid with life cycle composed zoospores, which attach to host, encyst, produce rhizoidal system (haustorium). Unlike typical Rhizophydiales chytrids, sporangium develops lateral outgrowth encysted zoospore. The ultrastructural study at least two unique traits: syringe-like organelle cyst, supposed paralyze funnel-shaped structure anchoring host wall. Sporangium matures produces zoospores 3 days. Multiple infections are common then 1–2 days shorter compared duration when single infection occurred. Cross-infection experiments showed E. could only infect dinoflagellates, being K. susceptible parasitoid. effects some fungal epidemics populations discussed.