A new species of Stephanostomum Looss, 1899 (Digenea, Acanthocolpidae) with a bizarre oral sucker: S. adlardi sp. nov. from the common coral trout Plectropomus leopardus (Lacepède, 1802) (Perciformes, Serranidae) from Lizard Island, Great Barrier Reef

Abstract A new species of Acanthocolpidae, Stephanostomum adlardi is described from the serranid Plectropomus leopardus from Lizard Island in the northern Great Barrier Reef. It differs from all previously described acanthocolpids in the structure of the oral sucker which is extended into dorsal and ventral lobes each bearing a row of spines. A phylogenetic tree estimated from combined nuclear small and partial large ribosomal RNA gene sequences shows that, despite the unusual oral sucker structure, the species is a true member of the genus Stephanostomum. The molecular results also suggest that Monostephanostomum nolani is derived from within Stephanostomum.