Fig. 5

Histological sections of gills of the common carp Cyprinus carpio infected by Myxobolus pseudoacinosus (narrow type). a Normal uninfected gill tissue with parallel filaments and intact gill lamellae. b Plasmodia of M. pseudoacinosus developing in the lumen of lamellar capillaries. c, d Higher magnification showing plasmodia located within the lumen of lamellar capillaries, pushing aside neighbouring lamellae (large arrows) and compressing the undifferentiated basal cells (arrowhead). The cartilaginous structure remains intact. Abbreviations: B, undifferentiated basal cells; CS, cartilaginous structure; F, gill filaments; NL, normal gill lamellae; OL, plasmodia-occupied gill lamellae; P, plasmodia; PL, gill lamellae become pushed aside; R, red blood cells. Scale-bars: a, b, 200 μm; c, d, 50 μm