Histological sections of shrimp gill tissue exhibiting various processes involved in the sBG infection and response processes. (A) The large ciliate at the right appears to be in close proximity to a forming nodule. (B) A ciliate contained within a cyst wall or membrane. (C) Remnants of a ciliate within a nodule. (D) A ciliate entrapped within a melanized nodule that appears to be undergoing necrosis. (H & E; each bar $ 50 mm).