Figure 2
From: Pathogenic lineage of Perkinsea associated with mass mortality of frogs across the United States
(a) Gross photograph of liver from Severe Perkinsea infection (SPI)-positive American bullfrog tadpole (Rana catesbeiana; NWHC #4824-453). Note that the liver is severely enlarged (hepatomegaly), approximately three times its normal size and exhibits pale-yellow discoloration. (b) Photomicrograph of liver from a non-infected Southern leopard frog tadpole (Rana sphenocephala; NWHC #18761-004), showing normal hepatic architecture. The arrows show normal hepatocytes forming hepatic cords. (c) Photomicrograph of liver from an SPI-positive Rana catesbeiana (NWHC #16407-009). Note that approximately 90% of the hepatic parenchyma is diffusely replaced by large numbers of Perkinsea-like protozoa. Arrows indicate few remaining, degenerating hepatic cords. (d) Photomicrograph of liver from SPI-positive Rana sphenocephala (NWHC #18967-001). Note that there are two distinct Perkinsea-like stages invading hepatocytes and causing degeneration, necrosis and disruption of hepatic cords; a spore-like stage, characterized by 4 to 6-µm diameter spherical structures with thick, deep basophilic wall, and granular pale basophilic cytoplasm (arrows); and a 1.8 to 3-µm diameter amoeboid, pale basophilic trophozoite-like stage (arrow heads). (e) Transmission electron photomicrograph of liver from an SPI-positive Rana catesbeiana (NWHC #16407-009). The cytoplasm of one hepatocyte (asterisk) is occupied by one Perkinsea-like spore (arrow) and two Perkinsea-like trophozoites (arrow head). In the extracellular space there are four trophozoite-like structures (arrow heads). Three of them are attached to the infected hepatocyte cell membrane.