ISKNV infection disrupted the sarcomeric Z disks of cardiomyocytes in mandarin fish. The structures of the sarcomeres and Z disks of cardiac muscle in PBS-injected control (A and B) and ISKNV-infected mandarin fish at 3 (C and D), 5 (E and F), and 7 (G and H) days postinfection are shown. Images in panels B, D, F, and H are higher magnifications of the boxed areas in panels A, C, E, and G. S*, sarcomeric structure.