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Morphological and pathological description of a new terrestrial eugregarine lineage infecting freshwater pearl mussels (Margaritifera margaritifera) in western Sweden
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology. (Burki lab)ORCID iD: 0000-0003-1733-4085
(English)Manuscript (preprint) (Other academic)
Abstract [en]

 Here, we report on the investigation of newly discovered gregarine lineages found infecting western Swedish populations of the freshwater mussel, M. margaritifera. This protist lineage, belonging to one of the terrestrial groups of gregarines (Eugregarinorida, Apicomplexa) was previously detected in a population of freshwater mussels that had been selected as control group in a previous study of mussel mortality events (MME). The MME had decreased the population of freshwater pearl mussels (FPM) in its sister population, by more than 60% within the same water catchment area. Even though no mortalities were reported from this control population, the population were not showing signs of ongoing recruitment, even if a there was trout population that could support a successful recruitment and distribution of FPM larvae. Our investigation indicated pathologies within the gonads and that these changes were associated to at least one type of gregarine infection, previously reported as lineage C from this creek. We describe the parasitic gregarine cell morphologies within gonads, foot and digestive gland and used CARD-FISH to link Lineage C sequence to protist cells and lesion associated in the host. This provides a promising method to infer disease associated lesions with environmental sequences.

Keywords [en]
Margaritifera margaritifera, Freshwater Pearl Mussel, Gregarine, reproductive disorder, vertical transmission, phylogeny, pathology, CARD-FISH
National Category
Natural Sciences
Research subject
Biology with specialization in Systematics
Identifiers
URN: urn:nbn:se:uu:diva-538791OAI: oai:DiVA.org:uu-538791DiVA, id: diva2:1899724
Funder
Swedish Research Council Formas, 2017-01197Available from: 2024-09-20 Created: 2024-09-20 Last updated: 2024-09-20
In thesis
1. Morphological and molecular studies of bivalves to assess the hidden diversity of protistan parasites: Investigations of cryptic diseases in shellfish
Open this publication in new window or tab >>Morphological and molecular studies of bivalves to assess the hidden diversity of protistan parasites: Investigations of cryptic diseases in shellfish
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates the host - parasitic relationships in mussel, started by investigating unexplained massmortalities in freshwater mussels, Margaritifera margaritifera. By compiling geodata with symptoms and histopathology (Paper 1). In Paper 2, I continued on these investigations, describing a parasitic gregarines in host. Using in situ hybridization (ISH) and ultrastructural analysis, we linked this gregarine to host detected lesions. To investigate fixed sampled, we used CARD-FISH demonstrating new patterns of parasitic infiltration of gonads. (Paper 3). In marine environments, protist parasites have been throughly documented, though several lesions remain unexplained. Using cell culture, we isolated Hexamita nelsoni linking this protist with blue mussels lesions in muscle & gonads, using CARD-FISH (Paper 4). The largest threat towards marine mussel aquaculture are Ascetosporean parasites, not culturable, requiring alternative methods for genomic studies. We used, density gradient filtration to concentrate Marteilia pararefringens and Bonamia ostreae from infected tissues, enabling these studies, Paper 5.

Abstract [sv]

Mitt doktorandsarbete undersöker relationen mellan musslan och dessa parasiter. Arbetet startade med studier av oförklarade massdödligheter bland sötvattens musslor, Margaritifera margaritifera, genom sammanställning av geologiska data och observerade sjukdomssymtom (Paper 1). In nästa studie (Paper 2), fortsätter vi detta genom att beskriva en ny gregarin (Apicomplexa) associerade med organförändringar. Med In situ hybridisering (ISH) och elektronmikroskopi, kunde vi koppla dessa till observerade vävnadsskador. Vidare påvisade vi olika arter av gregariner genom CARD-FISH metodik i histologiska prover och demonstrera därigenom nya mönster av parasitär infiltration (Paper 3). Mussel parasiter i marin miljö är  väldokumenterade, även om vissa organskador förblivit oförklarade. Genom cellkultur från blåmussla isolerades Hexamita nelsoni, och kopplades till observerade organskador, i muskel och gonadvävnad, med CARD-FISH (Paper 4). Det största hoten mot vattenbruk av Bivalver är Ascetosporea parasiter, som ej går at odla. För genomisk undersökning krävs andra alternativ. Med gradient filtrering  möjliggjordes koncentration av dessa celler och genomiska studier av Marteilia och Bonamia.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2024. p. 69
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2450
Keywords
Margaritifera margaritifera, Freshwater Pearl Mussel, Mass mortality events, Gregarine, Pathology, CARD-FISH, ISH, Mytilus edulis, blåmussla, Hexamita nelsoni, phylogeny, histology
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-538623 (URN)978-91-513-2233-9 (ISBN)
Public defence
2024-11-01, Lindahlsalen, 05.01058, Evolutionsbiologiskt centrum (EBC), Norbyvägen 14, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2024-10-11 Created: 2024-09-18 Last updated: 2024-10-31

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CiteExportLink to record
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Citation style
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