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Diseases of Aquatic Organisms

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DAO 153:31-43 (2023)  -  DOI: https://doi.org/10.3354/dao03718

Parasites and their impact on thick-shelled river mussels Unio crassus from two populations in Luxembourg

E. Lewisch1,*, F. Arnold1, H. P. Fuehrer2, J. Harl3, F. Thielen4, M. El-Matbouli1

1Clinical Division of Fish Medicine, University of Veterinary Medicine, 1210 Vienna, Austria
2Institute of Parasitology, University of Veterinary Medicine, 1210 Vienna, Austria
3Institute of Pathology, University of Veterinary Medicine, 1210 Vienna, Austria
4natur & ëmwelt/ Fondation Hëllef fir d’Natur, 9454 Kierchestrooss, Luxembourg
*Corresponding author:

ABSTRACT: The thick-shelled river mussel Unio crassus Philipsson, 1788 is a species native to many European habitats, with declining populations. The impact of parasite communities on health status of this species is poorly understood. In this study, parasites of 30 U. crassus specimens from the Our and Sauer Rivers in Luxembourg were identified morphologically and, in some cases, using molecular genetic methods. The findings were correlated to selected parameters (total length, visceral weight, shell lesions, gonadal stage). The 2 populations did not differ in shell length, visceral weight, number of males and females, gonadal scoring, shell lesions, and the occurrence of glochidia. The prevalence and infestation intensities of detected Trichodina sp., Conchophthirus sp., and freshwater mite larvae did not differ between the 2 populations, whereas the prevalence and infestation intensities of mite eggs, nymphs, and adults were significantly higher in the Sauer River. Rhipidocotyle campanula and European bitterling Rhodeus amarus larvae were only present in the Sauer. Histopathology revealed the destruction of the gonads by R. campanula and tissue damage by the mites. The only significant correlation of the selected parameters was a positive correlation between R. amarus occurrence and total length as well as a negative correlation between R. amarus occurrence and gonadal stage. In the Sauer River, 2 mussels were found to be hermaphrodites.


KEY WORDS: Trichodina · Conchophthirus · Rhipidocotyle campanula · Rhodeus amarus · Freshwater mite · Unionicola sauerensis · Histology · PCR · Hermaphrodite · Gonad staging


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Cite this article as: Lewisch E, Arnold F, Fuehrer HP, Harl J, Thielen F, El-Matbouli M (2023) Parasites and their impact on thick-shelled river mussels Unio crassus from two populations in Luxembourg. Dis Aquat Org 153:31-43. https://doi.org/10.3354/dao03718

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