Fig. 1

Histological sections of brown trout posterior kidney. a Tetracapsuloides bryosalmonae-exposed posterior kidney section shows T. bryosalmonae (arrows) proliferation, pronounced tubular degeneration and reduction of melanomacrophages at 12 weeks post-exposure (H&E staining). b Immunohistostaining shows interstitial extrasporogonic stages of T. bryosalmonae (arrows) in the posterior kidney. c No parasite or any renal changes were observed in the unexposed posterior control kidney (H&E staining). Scale-bars: 20 µm