Table 1.
Heterosporis-positive fish submitted to the Minnesota Veterinary Diagnostic Laboratory from 2009–2010.
All samples were confirmed by gross lesions, light microscopy, and sequence analysis. Fish were collected by hook and line recreational fishing.
Fig 1.
Heterosporis-positive fish submitted to the Minnesota Veterinary Diagnostic Laboratory from 2009–2010.
A) Walleye (Sander vitreus) 29.2 cm long. B) Yellow perch (Perca flavescens) 16.3 cm long. Arrows indicate sites of Heterosporis-induced lesions, with multifocal to coalescing necrosis of muscle tissue.
Fig 2.
A) Fresh preparation of microsporidia-infected fish. Arrow indicates a spore of Heterosporis sutherlandae n. sp. Arrowhead shows a sporophorous vesicle with several spores. B) Widespread muscle destruction due to H. sutherlandae. Mature spores have replaced muscle cells and are surrounded by loose fibrous tissue (asterisk). The wide arrow indicates a large sporophorocyst containing sporoblast and spores. The narrow arrow shows ruptured sporophorocyst vesicles. Tissue embedded in paraffin and stained with PAS. Scale bar is 100 μm. Inset: Giemsa stained preparation showing a detail of the wall of a sporophorocyst (wide arrow) and the wall of a sporophororous vesicle (arrowhead). Scale bar is 25 μm. C) Sporophorocysts (asterisk) within skeletal muscle cells (sm). Arrows indicate the sporophorocystic wall. Tissue embedded in resin and stained with Toluidine blue. Scale bar is 12 μm.
Fig 3.
Transmission electron microscopy of microsporidian granulomatous myocytis in a yellow perch.
A) Multiple mature spores (asterisk) at various stages of digestion (wide arrow) and cell and parasitic debris inside macrophages (m) and a muscle cell (sm). Scale bar is 5 μm. B) Multiple mature spores (asterisk) at various stages of digestion are inside parasitophorous vacuoles and phagolysosomes of macrophages (wide arrow). Spores display a spore wall and posterior vacuoles (white arrow). Nucleus (n) of macrophage. Scale bar is 5 μm.
Fig 4.
Heterosporis sutherlandae n. sp. from yellow perch and walleye.
A) Sporophorocyst containing several sporophorous vesicles. The sporophorocyst is lined by a thick wall (double headed arrow). The inner surface of the sporophorocyst is indicated by arrows. The edge of the wall of one sporophorous vesicle is highlighted by arrowhead. Spore is marked by an asterisk. Scale bar is 2 μm. B) Magnification of the sporophorocyst wall (double headed arrow) in a muscle fiber (mf); note the thick external layer, which is formed of microtubules and filaments (tf) and an inner electron dense membrane (arrow). The most internal smooth electron dense layer is a sporophorous vesicle, which is formed of an electron dense amorphous material (white arrowhead). A sporoblast (sb) is near the wall of the sporophorous vesicle. Scale bar is 1 μm. C) Spore wall (sw) of 122–137 nm comprised of an electron dense exospore (ex) measuring 20.78–33.98 nm and an electron lucent endospore (en) measuring 101.76–103.36 nm. Scale bar is 200 nm. D) Longitudinal section of H. sutherlandae displaying a spore wall (wide arrow), posterior vacuole (Pv), coiled filament (white arrowhead), polar filament (white arrow), nucleus (N), and anterior polaroplast. Scale bar is 0.5 μm. Inset: Anchoring disk of a spore. Scale bar is 200 nm. E) Transverse section of the anterior pole of H. sutherlandae displaying a spore wall (wide arrow), polar filament (white arrow), and anterior (Pa) and posterior polaroplast (Pp). Scale bar is 200 nm. F) Longitudinal section of coiled filament of H. sutherlandae. Scale bar is 200 nm. G) Transverse section of polar filaments of H. sutherlandae showing a concentrically multilayer structure. Spore wall (sw). Scale bar is 200 nm.
Table 2.
Comparison of Heterosporis species infecting fish.
Fig 5.
Phylogenetic analysis based on the 3,646bp nearly complete ribosomal RNA gene of Heterosporis sp., corresponding to nucleotide positions 170 to 3,815 of reference sequence AF387331.
The Maximum Likelihood phylogenetic tree was constructed using the General Time Reversible (GTR) model of nucleotide substitution (4 gamma categories) with 1,000 bootstrap replicates.
Fig 6.
Phylogenetic analysis based on a 1,200 bp nucleotide sequence, corresponding to nucleotide positions 600 to 1,800 of reference sequence AF387331.
The Maximum Likelihood phylogenetic tree was constructed using the General Time Reversible (GTR) model of nucleotide substitution (4 gamma categories) model with 1,000 bootstrap replicates.