Experimentally induced glochidiosis in smallmouth bass (Micropterus dolomieu)

Necropsy was performed on 2 smallmouth bass (Micropterus dolomieu) that died 8 days after experimental gill inoculation with Actinonaias pectorosa glochidia. The salient feature at necropsy was ragged gills containing multiple petechial hemorrhages and numerous white, iridescent dust-like particles easily confirmed as glochidia in squash preparations of the gill filaments. Microscopically, the gills contained multiple rounded glochidia encysted at the tips or along the length of the filaments. Parasitized filaments were thickened, blunted, and often fused. Lamellae were extensively fused and obliterated, with proliferation of the epithelial cells giving the filament a smooth outline. Sometimes glochidia were associated with necrosis and/or hemorrhage. These fish most likely died due to asphyxia associated with the severe branchial lesions caused by the glochidia.