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A Novel Gonadotropic Microsporidian Parasite (Microsporidium clinchi n. sp.) Infecting a Declining Population of Pheasantshell Mussels (Actinonaias pectorosa) (Unioinidae) from the Clinch River, USA

January 7, 2022

Freshwater mussels of the order Unionida are among the most endangered animal groups globally, but the causes of population declines are often enigmatic with little known about the role of disease. In 2018, we collected wild adult pheasantshell (Actinonaias pectorosa) and mucket (Actinonaias ligamentina) during an epidemiologic survey investigating an ongoing mussel mass mortality event in the Clinch River, USA. Histopathology and transmission electron microscopy showed a novel microsporidian parasite primarily infecting the ovary of pheasantshell. Sequencing of the small subunit rRNA gene produced a 1333 bp sequence with greatest similarity to Pseudonosema cristatellae (AF484694.1; 86.36%; e-value = 0), a microsporidium infecting the freshwater bryozoan (Cristatella mucedo). Microsporidia were observed in 65% (17/26) of the examined female pheasantshell (A. pectorosa) and in no (0/2) female mucket (A. ligamentina), and occurred at mortality and non-mortality sites. Our findings indicate that a novel parasite, Microsporidium clinchi n. sp., is present in pheasantshell in the Clinch River, USA, and while likely not a cause of mass mortality, could reduce fecundity and recruitment in this declining population and threaten the success of reintroductions. Surveillance for M. clinchi n. sp. and evaluation of brood stock and their progeny for microsporidia would therefore be prudent.

Publication Year 2022
Title A Novel Gonadotropic Microsporidian Parasite (Microsporidium clinchi n. sp.) Infecting a Declining Population of Pheasantshell Mussels (Actinonaias pectorosa) (Unioinidae) from the Clinch River, USA
DOI 10.5066/P9U4RYE1
Authors Susan Knowles, Eric M. Leis, Jordan C. Richard, Rebecca A Cole, Rose E. Agbalog, Joel G Putnam, Tony L. Goldberg, Diane L Waller
Product Type Data Release
Record Source USGS Digital Object Identifier Catalog
USGS Organization National Wildlife Health Center