Ultrathin sections of the underlying epidermis of the cuticle from shrimp with white spot syndrome viewed under the electron microscope revealed numerous non-occluded baculo-like viral particles in the necrotic areas. Hypertrophied nuclei filled with virions were also readily seen (Fig. 3). The virion was fusiform or rod-shaped with bluntly rounded ends. In negatively stained preparations, the virion was 70 to 150 nm at its broadest point, and was 250 to 380 nm long, 10% larger than is usually seen in ultrathin sections.In some virions, a tail-like projection extending from one end was observed (Fig. 4).