Fig. 1

Heterogeneity and different susceptibility to CaHV among three gibel carp clones. a Morphological difference among clone A⁺, F and H. b Transferrin phenotype patterns of three clones with three replications. c Symptoms in diseased fish. Hyperemia at the base of the fins and on the abdomen (black arrows), bleeding gills and internal organ hemorrhaging. d Cumulative mortality after CaHV infection. The values are the mean ± SEM from three replicate tanks. Asterisks (*) indicate significant differences (P ≤ 0.05) between clone A⁺ or clone F and clone H. e Histopathological photographs of head-kidney from normal and diseased gibel carp (HE). Healthy fish showed no pathological changes, while CaHV infected fish showed that the head-kidney appeared necrotic lesions (asterisk), serious vacuolization (black triangle), and hypertrophied nuclei with karyorrhexis (blue triangle). Scale bars = 100 um