Myxozoa + Polypodium: A Common Route to Endoparasitism.

Recent evidence places the problematic Polypodium, a parasite of fish eggs, firmly as sister taxon to Myxozoa within the Cnidaria. This resolution suggests a single route to endoparasitism in Cnidaria, with larval stages of a common ancestor exploiting fish as first hosts. It also enables new interpretations and insights regarding evolutionary transitions associated with endoparasitism.