A description of Lecithocladium invasor n.sp (Digenea : Hemiuridae) and the pathology associated with two species of Hemiuridae in acanthurid fish

Lecithocladium invasor n.sp. is described from the oesophagus of Naso annul atus, N. tuberosus and N. vlamingii on the Great Barrier Reef, Australia. T he worms penetrate the oesophageal mucosa and induce chronic transmural nod ular granulomas, which expand the full thickness of the oesophageal wall an d protrude both into the oesophageal lumen and from the serosal surface. We observed two major types of lesions: large ulcerated, active granulomas, c onsisting of a central cavity containing a single or multiple live worms; a nd many smaller chronic fibrous submucosal nodules. Small, identifiable but attenuated, worms and degenerate worm fragments were identified within som e chronic nodules. Co-infection of the posterior oesophagus of the same Nas o species with Lecithocladium chingi was common. L. chingi is redescribed f rom N. annulatus, N. brevirostris, N. tuberosus and A vlamingii. Unlike L. invasor n.sp., L. chingi was not associated with significant lesions. The d ifferent pathenogenicity of the two species in acanthurid fish is discussed .