Host switching in the Anguillicolidae. Cladograms of the eel genus Anguilla (left tree, blue)  and its swim bladder parasites, the family Anguillicolidae (Nematoda: Anguillicoloidea) (right tree, green). The known host parasite relationships are indicated by: black lines = traditional host-parasite relationship, displaying low abundances and low pathogenicity (parasite endemic in host); red lines = novel host-parasite relationship, displaying high abundances and pathogenicity; orange lines = novel host-parasite relationship, displaying low abundances and pathogenicity; dashed orange lines = novel host-parasite relationship where completion of the life cycle has not been demonstrated.
Laetsch et al. BMC Evolutionary Biology 2012 12:60 doi:10.1186/1471-2148-12-60