A thick shelled river mussel (Unio crassus).

Lea SchneiderAnders Nilsson, and Martin Österling from Karlstad University, and Johan Höjesjö from University of Gothenburg, recently published the scientific article “Local adaptation studies and conservation: Parasite–host interactions between the endangered freshwater mussel Unio crassus and its host fish in Aquatic Conservation. In the article the authors present a study on thick shelled river mussels (Unio crassus) and their interaction with potential host fishes originating from the same or a different river than the individual mussels. In the abstract they write:

“1. Parasite–host interactions can involve strong reciprocal selection pressure, and may lead to locally adapted specializations. The highly threatened unionoid mussels are temporary parasites on fish, but local adaptation has not yet been investigated for many species.

2. Patterns of local adaptation of one of Europe’s most threatened unionoids, the thick-shelled river mussel (Unio crassus) were investigated. Eurasian minnows (Phoxinus phoxinus) from two rivers (separate drainage areas) were cross-infested in the laboratory with sympatric and allopatric mussel larvae, while bullheads (Cottus gobio), inhabiting only one of the rivers, were infested with sympatric or allopatric mussel larvae. Larval encystment, juvenile mussel excystment and survival were measured.

3. For one river, but not the other, juvenile excystment from P. phoxinus was highest when infested with sympatric mussels. The opposite pattern was found for C. gobio in this river, where juvenile excystment and post-parasitic juvenile survival from allopatric C. gobio were highest. The results thus cannot confirm local adaptation of U. crassus to P. phoxinus in the study rivers, as excystment was not consistently higher in all sympatric mussel–host combinations, whereas there were potential maladaptive signs of U. crassus in relation to C. gobio. There was no loss of encysted larvae 3 days after infestation until juvenile excystment. Most juveniles were excysted between 17 and 29 days after infestation, and the numbers of excysted juveniles increased with fish size.

4. The results have implications for parasite–host ecology and conservation management with regard to unionoid propagation and re-introduction. This includes the need to (1) test suitability and adaptation patterns between U. crassus and multiple host fish species, (2) evaluate the suitability of certain unionoids and host fish strains after more than 3 days, and (3) determine whether large fish produce more juvenile mussels than smaller fish.”

Access the paper here: “Local adaptation studies and conservation: Parasite–host interactions between the endangered freshwater mussel Unio crassus and its host fish“, or email any of the authors.


Caryn Vaughn (left) asking questions to Lea Schneider (right) during the PhD-defense.

Today Lea Schneider successfully defended her PhD-thesis ”Conservation ecology of the thick-shelled river mussel Unio crassus – the importance of parasite-host interactions” at Karlstad UniversityCaryn Vaughn (University of Oklahoma, USA) was the opponent, and Leonard Sandin (Swedish University of Agriculture), Niklas Janz (Stockholm University, Sweden), and Annie Jonsson (University of Skövde, Sweden) constituted the grading committee (betygskommitté).

Lea Schneiders supervisors during her PhD were Martin Österling and Anders Nilsson from Karlstad University, and Johan Höjesjö from the University of Gothenburg, Sweden. Her work constituted on part of the LIFE-project UCforLife – Målarmusslans återkomst.

The thesis is available here. Contact Lea Schneider for questions and additional information.

DrWatzFör en dryg vecka sedan disputerade Johan Watz med avhandlingen ”Salmonid behaviour under winter conditions”. Kappan kan läsas online här. Avhandlingens publicerade artiklar är följande:

Paper I: Ice cover affects the growth of a stream-dwelling fish

Paper II: Effects of ice cover on the diel behaviour and ventilation rate of juvenile brown trout

Paper III: Day and night drift-feeding by juvenile salmonids at low water temperatures

Paper IV: Prey capture rates of two species of salmonids (Salmo trutta and Thymallus thymallus) in an artificial stream: effects of temperature on their functional response

Paper V: Ice cover alters the behavior and stress level of brown trout Salmo trutta

Opponent var Richard Cunjak från University of New Brunswick och i betygskommitten satt Nina Jonsson (NINA), Johan Höjesjö (Göteborgs Universitet) och Asbjørn Vøllestad (Universitetet i Oslo).

Under doktorandtiden handleddes Johan Watz av Larry Greenberg, Eva Bergman och John Piccolo.