Histopathology of the gastrointestinal tract, digestive gland and gonads.

<p>(A) Normal histology of the stomach epithelium and the adjacent digestive gland tubules. Note the firm connective tissue layer (CT) separating the stomach wall and the digestive gland tubules. (B) Histological sections through the stomach and the digestive gland of a heavily infected scallop showing extensive accumulation of apicomplexan zoites in connective tissues surrounding the stomach epithelium and in the digestive gland interstitium causing separation of the basement membrane (black arrow) from the stomach epithelium (EP) and necrosis of the connective tissues and digestive cells (white arrows). (C) A total destruction the digestive gland associated with mixture of cellular debris and numerous apicomplexan zoites (*). The stomach epithelium (EP), connective tissues and digestive cells (white arrows) are heavily necrotized. (D) Higher magnification of the area within the black square of (D) showing apicomplexan zoites. (E and F) Female gonads from scallops caught in early May 2005. A normal one (E), with large acini filled with semi-mature eggs, and a diseased one (F) where the inter-acinal tissues are massively infected with apicomplexan zoites which have caused a total destruction of the acini in large areas (*). The remaining acini have merely premature eggs (arrows) and their development asynchronous with time of year. (G) Higher magnification of the area within the black square of (F) showing apicomplexan zoites (arrow). (H) Section through a heavily infected gonad and intestine of a male scallop. The connective tissue surrounding the intestinal epithelium and inter-acinal tissues are heavily infected with apicomplexan zoites causing the basement membrane to separate from the epithelial lining (broad arrow) and degeneration of the epithelial cells (EP). The apicomplexan causes destruction of the connective tissue which makes up the wall surrounding the acini which subsequently decay (thin arrows). (I) Higher magnification of the area within the black square of (H) showing apicomplexan zoites. Abbreviations. EP = Epithelial layer; IL = Intestinal lumen; SL = Stomach lumen.