Cytopathology of Bay of Piran shrimp virus (BPSV), a new crustacean virus from the Mediterranean Sea.

A new picorna-like or parvo-like virus was found in the hepatopancreas of the shrimp Palaemon elegans from the Bay of Piran (Mediterranean Sea). Bay of Piran shrimp virus (BPSV) infects preferably the R-cells of the hepatopancreas and to a lesser extent the F-cells. In R-cells it is abundant in the cytoplasm and within membrane whorls. In lesser numbers it can also be present in cell organelles like the endoplasmic reticulum, autophagosomes, or mitochondria. Less contrasting virus-like particles are observed in the nucleoplasm, suggesting a nuclear replication of the virus and completion of assembly in the cytoplasm. In F-cells the virus is located mostly in cisternae of the Golgi bodies. Occasionally, there are also virus clusters in the cytoplasm. B-cells are only rarely infected. The virus seems to invade the host cells from the lumen of the hepatopancreatic tubules through the microvillous border. Mature viruses are released again into the hepatopancreatic lumen by discharge of lytic epithelial cells. Individual viruses can also penetrate through the basal cell membrane into the hemal space. Occasionally, fixed phagocytes are attached to the basal lamina of heavily infected hepatopancreas cells, indicating an activation of the immune defense system by the virus.