The surface ultrastructure of mature egg chorion of the tamed northern sheatfish Silurus soldatovi in Heilongjiang river was investigated by scanning electron microscopy. The outermost layer was composed of a thin lamella of a jelly coat. The surface of jelly coat was characterized by overlapping net-like fibrillar lamellae, many clefts with bridges and pores. The pore canals were 0.25 μm in diameter. The pore density was about 0.7-1.0/μm-2. The pores on the surface of jelly coart were distributed uniformly. Mature eggs of sheatfish possessed a funnel-shaped micropyle in the animal polar region. The micropylar region was about 0.04 mm2 area in diameter with 3-8 ridges in radial arrangement. Fertilized eggs in which jelly coats were removed mechanically presented no adhesiveness and exhibited inlays of irregular granules on their surface.
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