Defense against parasites in fish: role of behaviour and refugia (--)

Main funder

Funder's project number: 326047

Funds granted by main funder (€)

  • 14 800,00

Funding program

Project timetable

Project start date: 01/03/2019

Project end date: 31/12/2022


Threats of predators and parasites play an important role in ecosystems (natural enemy ecology). Typically a variety of different
enemies, including predators and parasites, simultaneously or sequentially attack any organism. This may lead to the trade-off between
anti-predator and anti-parasite activities.
We will experimentally study interactions between fish behaviour related to vulnerability to parasites (activity, aggressiveness,
shoaling), habitat complexity and parasite risk at individual and population levels. Juvenile rainbow trout, Oncorhynchus mykiss (host)
and eye fluke, Diplostomum pseudospathaceum, (parasite) study system will be used in our experiments. These species are widely used
in studies on behavioural and ecological aspects of host-parasite interactions. Juvenile O. mykiss can switch from shoaling to
territoriality demonstrating either cooperative or agonistic behaviour. The role of a natural enemy of parasites in our study will belong
to bivalve mollusk Anodonta anatina.
Hypothesis 1. We expect that fish will acquire different numbers of parasites according to the level of the habitat complexity. More
precisely, we suggest that infection intensities in fish will be lower in the presence of alive mussels ('active' refugium) than in the
presence of their empty shells ('passive' refugium) or in the environment without refugia.
Hypothesis 2. Habitat structure will influence fish behavioural traits related to their potential vulnerability to parasites (e.g. fish activity,
aggressiveness and/or shoaling behaviour). In the presence of shelters fish will be more aggressive. Aggressiveness will be highest in
the presence of alive bivalve mollusks, because environment in this treatment is the safest, cause the risk of infection will be the lowest
due to filtering activity of mussels.
Hypothesis 3. Complexity of environment influences not only the average infection intensities of a population but also betweenindividual
variation. We expect higher variability in heterogeneous habitats where losers in the competition for a territory are more
infected than the winners.
Hypothesis 4. If there is a conflict between anti-parasitism and anti-predation behaviours, individuals should avoid anti-predation
behavior when there is an increased risk of parasitism. We expect relaxation of anti-predation behavior (freezing) when fish are exposed
to parasite larvae—excape from the vicinity of parasites will overrule freezing (predation avoidance).

Principal Investigator

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Last updated on 2023-06-02 at 15:53