Hirsutonosema embarrassi n. gen. n. sp. (Phylum Microsporidia) in the Ovary of Mucket (Actinonaias ligamentina), Plain Pocketbook (Lampsilis cardium), and Fatmucket (Lampsilis siliquoidea) (Unionidae) from the Embarrass River, Wisconsin, USA

Parasitologia
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Abstract

During an epidemiological survey following a mortality event of freshwater mussels in 2018 in the Embarrass River, Wisconsin, USA, we identified a novel microsporidian parasite in the ovaries of mucket (Actinonaias ligamentina), plain pocketbook (Lampsilis cardium), and fatmucket (Lampsilis siliquoidea) (Unionidae). Histopathology showed round-to-oval microsporidian spores in the cytoplasm of oocytes in 60% (3/5) of female mucket, 100% (4/4) of female plain pocketbook, and 50% (1/2) of female fatmucket. Using transmission electron microscopy, we found that mature spores were round-to-oval and measured 4.13 ± 0.64 µm (3.14–5.31) long by 2.88 ± 0.37 µm (2.36–3.68) wide. The spores had a thin electron-dense exospore with a spiky “hairy” coat, a thick electron lucent endospore, diplokaryotic nuclei, a polar vacuole, and 27–28 polar filaments arranged in 1–3 rows. Sequencing of the small subunit rRNA produced a 1356 bp sequence most similar to that of Pseudonosema cristatellae (92%), and phylogenetic analysis grouped it within the freshwater Neopereziida. Genetic, morphological, and ultrastructural characteristics did not closely match those of other Pseudonosema spp., and a new genus and species, Hirsutonosema embarrassi n. gen. n. sp., were designated. Additional studies could evaluate host susceptibility, distribution, seasonality, transmission, and lethal or sub-lethal effects of this parasite on freshwater mussels.
Publication type Article
Publication Subtype Journal Article
Title Hirsutonosema embarrassi n. gen. n. sp. (Phylum Microsporidia) in the Ovary of Mucket (Actinonaias ligamentina), Plain Pocketbook (Lampsilis cardium), and Fatmucket (Lampsilis siliquoidea) (Unionidae) from the Embarrass River, Wisconsin, USA
Series title Parasitologia
DOI 10.3390/parasitologia4020016
Volume 4
Issue 2
Year Published 2024
Language English
Publisher MDPI
Contributing office(s) National Wildlife Health Center
Description 15 p.
First page 184
Last page 198
Country United States
State Wisconsin
Other Geospatial Embarrass River
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