Bacterial diseases of eggs and yolk sac larvae of halibut (Hippoglossus hippoglossus L.): Characterization and experimental infection

Abstract

Scanning electron micrographs of halibut eggs which were shown to have an epiflora dominated by a Flexibacter sp., revealed wounds colonized by large amounts of bacteria. The chorion was penetrated in most wounds, and the zona radiata was severely damaged. Infection experiments showed that exposure to these bacteria caused high mortality at hatching and early yolk sac stage. Eggs exposed to strains of Vibrio anguillarum and Vibrio fisheri showed a different mortality pattern, with low mortality at hatching, followed by a continuous high mortality throughout the yolk sac stage. Mortality in the uninfected control group was low throughout the experiment.