Sporogony of Tetracapsuloides bryosalmonae in the brown trout Salm trutta and the role of the tertiary cell during the vertebrate phase of myxozoan life cycles

Citation

Morris D & Adams A (2008) Sporogony of Tetracapsuloides bryosalmonae in the brown trout Salm trutta and the role of the tertiary cell during the vertebrate phase of myxozoan life cycles. Parasitology, 135 (9), pp. 1075-1092. https://doi.org/10.1017/S0031182008004605

Abstract
Tetracapsuloides bryosalmonae is the myxozoan that causes the commercially and ecologically important proliferative kidneydisease of salmonid fish species. Immunohistochemistry and electron microscopy were used to examine the developmentof this parasite within the kidney of the brown trout Salmo trutta. The main replicative phase of T. bryosalmonae is a celldoublet composed of a primary cell and a single secondary cell. Engulfment of one secondary cell by another to form asecondary-tertiary doublet (S-T doublet) heralded the onset of sporogony whereupon the parasite migrated to the kidneytubule lumen. Within the tubule, the parasite transformed into a pseudoplasmodium and anchored to the tubule epithelialcells via pseudopodial extensions. Within each pseudoplasmodium developed a single spore, composed of 4 valve cells,2 polar capsules and 1 sporoplasm. The pseudoplasmodia formed clusters suggesting that large numbers of spores developwithin the fish. This examination of T. bryosalmonae suggests that the main replicative phase of freshwater myxozoanswithin vertebrates is via direct replication of cell doublets rather than through the rupturing of extrasporogonic stages,while tertiary cell formation relates only to sporogony. Taken in conjunction with existing phylogenetic data, 5 distinctsporogonial sequences are identified for the Myxozoa.

Keywords
Tetracapsuloides; PKX; PKD; Malacosporea; Myxosporea; Buddenbrockia; Sphaerospora; Kudoa; Myxozoa; ultrastructure

Journal
Parasitology: Volume 135, Issue 9