Fig. 3

Histology of infections by Accacoelium contortum in gills of the ocean sunfish Mola mola (L.) from the Western Mediterranean. a Uninfected gills (b refers to area magnified in (b); scale bar = 100 μm. b Gill epithelium without secondary bacterial infections (stained with Giemsa); scale bar = 10 μm. c Gills showing the parasite (arrow) surrounded by large papillary folds (e and f indicate the areas of infection magnified in e and f, respectively); scale bar = 200 μm. d Secondary bacterial infections (asterisks) in the gill epithelium associated with A. contortum infections (stained with Giemsa); scale bar = 10 μm. e Detail of Fig. 3c showing the area of the gill tissue in contact with the parasite surface with thick pale-pink layer (white star) and pyknotic necrotic epithelial cells (black star); scale bar = 50 μm. f Detail of (c) showing the outer dense homogeneus layer covering parasite tegument (arrows) (inset: enlarged papilla showing a detail of this layer); scale bar = 50 μm (inset 10 μm). Stained in H-E, except for (b and d)