A thick-shelled river mussel, Unio crassus

Between 2012 and 2016, researchers at Karlstad University have worked together with several county boards in southern Sweden in the EU-funded life project “Unio crassus for life” (målarmusslans återkomst). The thick-shelled river mussel (Unio crassus) is one of the most threatened bivalve species in Europe. In Sweden, the distribution of the species has decreased with 50% over the last 100 years.

In twelve streams in southern Sweden, a total of 300 km has been restored as part of the project to improve the habitat for the mussel. The project has also examined what fish species that are suitable hosts for the obligate parasitic larvae of the thick-shelled river mussel. Species like minnow (Phoxinus phoxinus), bleak (Alburnus alburnus) and bullhead (Cottus gobio) seem to be important hosts for the mussel. In addition, juvenile mussels have been reared in captivity with the aim to successfully reintroduce them into the wild.

The project has been very successful, and has now been nominated as one of the best EU life projects. The ceremony where the best project will be awarded is held in Brussels 23 May. Martin Österling, associate professor at Karlstad University, will attend the ceremony. We wish Martin and all other people that have worked on the Unio crassus for life project the best of luck, and we keep our fingers crossed that Unio crassus for life will be awarded the best EU life project.

Read more about the project at the Unio crassus for life official web page, or on the Skåne and Södermanland county board web pages.

The project has also gotten publicity in media, and you can read more about the project on svt or Smålands-tidningen.

Watch a short film about the project here.

A thick-shelled river mussel (Unio crassus).

NRRV is looking for a part-time project assistant to work with the endangered thick-shelled river mussel (Unio crassus). The project concerns rearing of juvenile mussels in the mussel lab in Veberöd, Skåne, and reintroduction of mussels in streams in southern Sweden. Read more and apply for the position here (Swedish). The last day to apply is 2 March 2018.

Adult thick shelled river mussel (Unio crassus) from the River Tommarpsån, Sweden.

Lea Schneider, Anders Nilsson, and Martin Österling from Karlstad University, recently published the scientific article “Evaluating temperature- and host-dependent reproduction in the parasitic freshwater mussel Unio crassus” in the journal Hydrobiologia. In the article they present a study on the thick shelled river mussel (Unio crassus) and its release of glochidia (mussel larvae) in different temperature regimes.

In the abstract they write: “Adaptation to temperature regimes and host presence may enhance fitness in parasites. In an experimental study, we evaluated the timing of glochidia release by Unio crassus subjected to three spring water temperature regimes in the presence and absence of the host fish Cottus gobio. The timing of glochidia release was delayed at (i) constantly low temperatures (<10°C), in contrast to earlier and pronounced releases at (ii) natural temperature increases that level off at intermediate temperatures (10–15°C), and (iii) higher-than-normal temperatures (10–20°C). Mussels from treatment (i) that had not released glochidia during the experiment did so soon after being moved to the temperature in (ii), indicating a temperature threshold for glochidia release. Neither host fish presence nor the combined effect of temperature and host fish presence significantly affected the timing of glochidia release. The treatment with natural spring water temperatures indicated possible fitness benefits for U. crassus through combined effects of high intensities of glochidia releases and high survival of released glochidia. The furthered understanding of climate change effects on mussel and host phenology in seasonal environments, potentially inducing temporal mismatches of glochidia release to host availability, is key to mussel conservation.”

Acces the paper here: Evaluating temperature- and host-dependent reproduction in the parasitic freshwater mussel Unio crassus

The research was part of the LIFE project UCforLIFE. Read more about the thick shelled river mussel and related conservation work at the projects homepage: www.ucforlife.se

According to tradition, Lea Schneider (center) last week nailed her thesis to the wall, at the entrance to Karlstad University. On the photo are also Martin Österling (supervisor) and Reine Lundin (dean).

On February 24, Lea Schneider, will defend her PhD-thesis “Conservation ecology of the thick-shelled river mussel Unio crassus – the importance of parasite-host interactions”. In the abstract Lea Schneider writes: “Unionoid mussels are globally threatened and their conservation requires species-specific knowledge on their ecology and parasite-host interaction. Unio crassus is one of Europe’s most threatened unionoid species and has a temporary obligate parasitic life stage (glochidia) on fish. A lack of suitable hosts is probably a major limitation for mussel recruitment, but host species composition, suitability and availability in time and space have yet to be fully explored. This thesis examines different aspects of the host fish species, including their composition, suitability and ecological importance, in relation to U. crassus, using both field and laboratory studies. The effects of mussel and host density on mussel reproductive potential were considered, as were aspects of evolutionary adaptations between mussels and fish and how climate change may affect their interaction.

The results show that U. crassus is a host generalist, parasitizing a variety of fish species. Host suitability and density, which varied among fish species and rivers, affected the level of glochidia encapsulation, hence mussel reproductive potential, more so than the density of mussels taking part in reproduction. Ecologically important hosts included both highly suitable primary hosts, and less suitable hosts that were highly abundant. Whether or not U. crassus has specific adaptations to its hosts to enhance juvenile transformation remains unclear. No distinct pattern of local adaptation was found, nor was there an effect of host fish presence on the timing of glochidia release by adult mussels. Instead, temperature played a major role, with results suggesting that changes in spring water temperature regimes can cause temporal and spatial mismatches in the mussel-host interaction. This thesis indicates that investigations of local mussel-host interactions help in identifying mechanisms important for unionoid conservation management and prioritization.”

The defense will take place on February 24 at 10:15 in room 1B309 (Sjöströmsalen) at Karlstad University. The frame of the thesis is available online here.

For the defense, Caryn Vaughn (University of Oklahoma, USA) is the opponent, and Leonard Sandin (Swedish University of Agriculture), Niklas Janz (Stockholm University, Sweden), and Annie Jonsson (University of Skövde, Sweden) constitute the grading committee (betygskommitté).

In the afternoon (from 13:30 onwards) the day before the defense (Feb 23), seminars related to the thesis will be given in Room 5F416 at Karlstad University. Here Caryn Vaughn will present on “Consumer aggregations act as hotspots of ecosystem function and services in rivers”, Niklas Janz on “What is host range?”, and Leonard Sandin on “Evaluation of ecological restoration in Swedish streams – some results from the EKOLIV project”. 

Everyone is welcome to attend both the PhD-defense and the seminars.

Klingavälsån i Skåne har restaurerats, delvis som en del av ett projekt att reintroducera den tjockskaliga målarmusslan i vattendraget. Restaureringen förväntas förbättra livsförhållandena för en mängd fiskar och andra vattenlevande organismer i ån. Som en del av utvärderingen av åtgärden elfiskas nu vattendraget och SVT-Skåne passade på att göra ett kort besök hos biologerna på plats. Bland flera andra fiskarter, hittades under dagen hittades Sveriges största rapporterade Grönling (Barbatula barbatula). Grönligen fick naturligtvis uppmärksamhet på TV. Se inslaget här:

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Om ungefär två veckor, den 28-30 September, arrangeras även “International River Restoration Conference” i Lund. Konferensen är en del av projektet att återintroducera målarmusslan (UCforLife), och förutom en mängd intressanta föredrag så står även studiebesök till bland annat Kingavälsån på programmet. Det är fortfarande möjligt att anmäla sig till konferensen. Läs mer och se mötets pogram här.

Martin Österling förevisar en tjockskalig målarmussla i samband med invigningen av den nyrestaurerade ån. Foto från Skånska Dagbladet.

För knappt två veckor sedan invigdes den nyligen restaurerade Klingaälsvån i Skåne. I en tidigare epok rätades vattendraget för att öka jordbruksproduktionen i området, nu har man återställt ett naturligt slingrande (meandrande) vattendrag. Restaureringen består, förutom återmeandring av vattendraget, också av försök att återetablera den tjockskaliga målarmusslan i ån. I slutändan förväntas åtgärden leda till ett mer naturlikt vattendrag och mindre läckage av jordbrukets näringsämnen till havet.

Den tjockskaliga målarmusslans larver lever som bekant en tid som parasiter på fiskars gälar. Som ett led av projektet har den tjockskaliga målarmusslans förhållande till olika fiskarter studerats. Forskningen om mussellarvernas förhållande till olika fiskarter har legat till grund för att fisk, såsom stensimpa och elritsa, fångats i ån, infekterats av mussellarver på lab och sedan åter släppts ut i ån. Från Karlstads Universitet har Lea Schneider och Martin Österling varit aktiva i projektet.

Läs mer om projektet på UCforLIFE.se. Skånska Dagbladet har också en artikel med flera foton från invigningsdagen. Läs den här.

UCforLife is a LIFE-project for river restoration and research related to the thick shellled river mussel (Unio crassus). Martin Österling, Lea Schneider, and Anders Nilsson at Karlstad University are involved in the project. The project is now announcing an upcoming international river restoration conference in Lund, Sweden, on 28–30 September. In the announcement they write:

“Conference objectives are to highlight experiences and results gained from a wide range of river restoration projects focusing on rehabilitation of species of freshwater mussels and fish. Mussels and fish are often used as indicators and flagship species while restoring rivers. But are they any good? If so – why? 

The first two days will focus on presentations by invited experts and conference participants who want to present their work. The third day includes field visits to Fyleån Creek, Klingavälsån River, both sites re-meandered,and the Hemmestorp Mölla rearing facility. 

Call for abstracts, oral or poster presentations, information about registration, fees etc will be available in July. We look forward to seeing you in Lund”

Lea Schneider, PhD-student at Karlstad University, is doing research on the thick shelled river mussel (Unio crassus) within the LIFE projekt UCforLife. The project, including both basic research and restoration efforts, is presented in this short Youtube video:

Filmen finns också tillgänglig på svenska här.

Kilaån in Södermanland. Foto från ucforlife.se

Lea Schneider rapporterar om den fortsatta forskningen på tjockskalig målarmussla. Nyligen har de elfiskat Kilaån och Svärtaån efter möjliga värdfiskar till musslan. Målarmusslans larv sitter ju under en period fast på fiskens gälar innan den släpper tagit och faller till botten. Under ett par dagar samlades en mängd fiskar in och transporterades till labb. På labbet hölls fiskarna i särskilda behållare i väntan på att eventuella juvenila musslor skulle släppa från fiskarnas gälar och sjunka till botten. Mussel-juveniler hittades tillsammans med löja (Alburnus alburnus), stensimpa (Cottus gobio), abborre (Perca fluviatilis), och gärs (Gymnocephalus cernuus). Musslorna har nu skickats på DNA-analys för att bestämma om det rör sig om tjockskalig målarmussla.

Läs mer på UCforLIFEs hemsida.

I Havs och Vattenmyndighetens tidning, Hav och Vatten, nr 5 2015, finns en artikel om återmeandringen av Klingälvsån i Skåne och projektet Målarmusslans återkomst. Den tjockskaliga målarmusslan är frontfigur för projektet som syftar till att återintroducera musslan, förbättra dess livsmiljö och vattenkvaliteten i tolv sydsvenska vattendrag. Även om musslan har huvudrollen i den här historien förväntas projektet få positiva effekter även för fisk och andra organismer i det rinnande vattnet. Från Karlstads Universitet arbetar Martin Österling och Lea Schneider inom projektet. Läs mer  på sidan 9 i tidningen!