Henneguya laseeae n. sp. from flathead catfish (Pylodictis olivaris) in the upper Mississippi River.

A novel species of Henneguya was isolated from flathead catfish (Pylodictis olivaris) captured in the upper Mississippi River near Lansing (Allamakee County), IA, and La Crosse (La Crosse County), WI. Designated Henneguya laseeae n. sp., this novel species is described using critical morphological features, histology, and 18S ribosomal RNA gene sequence. Ovoid cysts, ranging from 1200 to 1800 μm in width, tended to be at filament tips or in the distal third, often directly on the filament midline, but occasionally paramedian. Lanceolate-shaped myxospores were consistent with those of the genus Henneguya. The spore body was 16.2 ± 0.5 μm (mean ± standard deviation; range = 15.1-17.0 μm) in length, 6.0 ± 0.4 μm (5.1-6.6 μm) in width, and 4.7 ± 0.2 μm (4.4-4.9 μm) thick. The two polar capsules at the anterior of the spore body were 5.9 ± 0.3 μm (5.3-6.3 μm) in length and 1.8 ± 0.1 μm (1.6-2.1 μm) in width and contained six to seven turns in the polar filament. The caudal processes tapered to fine points and were 54.3 ± 2.9 μm (49.1-61.7 μm) in length. Total spore length was 70.4 ± 3.3 μm (64.5-79.4 μm). The spores and plasmodium of this species are of similar size and morphology to other species of Henneguya from ictalurid fishes. Additionally, the 18S rRNA gene sequences placed this isolate within a clade populated by Henneguya spp. from North American ictalurids. This is the first reported species of Henneguya from flathead catfish.