Light micrographs of gill morphology of adult zebrafish exposed to maduramicin for 14 days (100 ×). (a) A control group exhibited normal structure, including a gill arch formed by filaments (F) and lamellae (SL); (b) gill exposed to 0.1 mg/L maduramicin exhibited normal histology; (c) gill exposed to 0.5 mg/L maduramicin exhibited slight epithelial lifting (EL) and lamellar fusion (LF); (d) gill exposed to 2.5 mg/L maduramicin exhibited serious epithelial lifting (EL), lamellar fusion (LF) and necrosis (N).

Light micrographs of liver morphology in adult zebrafish treated by maduramicin for 14 days (400 ×). (a) A control group exhibited normal structure; (b) liver treated by 0.1 mg/L maduramicin exhibited no obvious histopathological lesion; (c) liver treated by 0.5 mg/L maduramicin exhibited peripherally located nucleus (black arrows) and slight vacuole formation (VF); (d) liver treated by 2.5 mg/L maduramicin exhibited peripherally located nucleus (black arrows), pyknotic nucleus (yellow arrows), and serious vacuole formation (VF). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Light micrographs of intestine morphology of adult zebrafish exposed to maduramicin for 14 days (100 ×). (a) A control group exhibited normal structure; (b) intestine exposed to 0.1 mg/L maduramicin exhibited normal histology; (c) intestine exposed to 0.5 mg/L maduramicin exhibited much more goblet cells (black arrow) than the control group; (d) intestine exposed to 2.5 mg/L maduramicin exhibited fracture of intestinal villus (yellow arrow). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)