Tissue reaction of the three-spined stickleback Gasterosteus aculeatus L. to infection with Glugea anomala (Moniez, 1887)

Abstract. Studies on an experimental infection of the stickleback (Gasterosteus aculeatus L.) with the microsporidian Glugea anomala conducted until day 126 post infection confirmed that xenoparasitic formations typical of the intracellular development of this microsporidian were responsible for a marked tissue reaction in the host. After a single oral infection, xenoparasitic formations developed in the subepithelial connective tissue of the glandular part of the stomach. The course of xenoma development was asynchronous. Up to the 'cyst' stage (xenomas filled with mature spores), their growth and development caused a pressure atrophy in the surrounding tissue. Later, the response to the presence of the xenoparasitic formation was the development of a granulomatous inflammatory reaction. Locally, the host responded to the infection by phagocytosis of mature spores by locally derived macrophages. In massive infections, changes occurred in the subepithelial connective tissue of the glandular part of the stomach (often the complete disappearance of tubular glands), which may result in a permanent influence on the function of this organ.