2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

S�5 Nina Schlotz R513 / 14:15
A dietary polyunsaturated fatty acid protects Daphnia against pathogenic threats
Authors: Nina Schlotz 1 , Dominik Martin-Creuzburg 1
Affiliation: 1 University of Konstanz
Dietary restrictions, both in quantity and quality, have been proposed to affect the
resistance of animals to pathogenic infections. Using an oral infection model
consisting of the freshwater herbivore Daphnia magna and the opportunistic
bacterial pathogen Pseudomonas sp. we explore the hypothesis that a dietary
deficiency in C20 polyunsaturated fatty acids (PUFAs) impairs the capability to cope
with pathogenic threats, because C20 PUFAs serve as precursors for eicosanoids
which in turn act in immunity of invertebrates and vertebrates. Survival, somatic
growth and reproduction of the host were recorded under different algal food
regimes which contained or were deficient in C20 PUFAs. We show that animals
feeding on a diet rich in C20 PUFAs are less affected by pathogen exposure and that
this effect is mediated mainly by a single dietary PUFA.
S�6 Eric von Elert R513 / 14:30
Evidence for inducible tolerance of Daphnia magna to cyanobacterial protease
inhibitors
Authors: Eric von Elert 1 , A. Zitt 1 , Anke Schwarzenberger 1
Affiliation: 1 University of Köln
The frequency of toxic cyanobacterial blooms has increased worldwide due to manmade
eutrophication. Daphnia has been shown to acquire tolerance to
cyanobacterial toxins on the population level and within an animals‘ lifetime,
however, the molecular basis of this is unknown. Among the most wide-spread
cyanobacterial secondary metabolites are protease inhibitors. Here we investigate if
these cyanobacterial inhibitors cause a reduction of food quality and if Daphnia
shows inducible tolerance to these inhibitors. We use a strain of the cyanobacterium
Microcystis aeruginosa, which contains known chymotrypsin inhibitors, the green
alga Scenedesmus obliquus as reference food and a clone of D. magna. When grown
on the green alga, three chymotrypsins in the mass range from 16 kDa to 22 kDa
were distinguished in D. magna. Already with 20% M. aeruginosa this pattern of
chymotrypsins changed. Feeding encapsulated purified cyanobacterial chymotrypsin
inhibitor induced the same changes in pattern and reduced the growth of D. magna
on the green alga. IC50 values for inhibition of chymotrypsins of D. magna by the
cyanobacterial inhibitors increased significantly when the cyanobacterium was part
of the diet in comparison to a pure green algal diet. We conclude that D. magna
acquires increased tolerance to cyanobacteria protease inhibitors within an animal‘s
lifetime by remodelling the digestive chymotrypsins. This mechanism might be
relevant for the transfer of tolerance to the next generation through maternal
effects.
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