Rearing temperature and fatty acid supplementation jointly affect membrane fluidity and heat tolerance in Daphnia

Dominik Martin-Creuzburg, Bret L. Coggins, Dieter Ebert, Lev Y Yampolsky

Preprint posted on April 06, 2018

Daphnia diet affects thermal tolerance

Selected by Alexander Little


Membrane fluidity plays major roles in cellular physiology, including membrane integrity, enzyme function and energy production. Warm temperatures promote membrane fluidity, whereas cold temperatures promote rigidity. Maintaining membrane fluidity therefore represents a major challenge faced by ectothermic (cold-blooded) animals in response to shifting thermal environments. But many animals can compensate for swings in temperature by remodelling relative proportions of mono- and polyunsaturated fatty acids (PUFA) that comprise plasma membranes (homeoviscous adapation; Sinensky 1974).

Most animals do not synthesize long-chain PUFAs de novo, but rather assimilate them via dietary means. This is interesting because it means resilience to temperature stress is likely influenced by nutritional development and diet. Here Martin-Creuzburg et al. test the hypothesis that rearing temperature and changes in dietary PUFA during development, by means of eicosapentaenoic acid (EPA) supplementation, have carryover effects on subsequent heat tolerance in the crustacean, Daphnia magna.


Key findings

In line with previous work, the authors find that membrane fluidity i) decreases with increasing rearing temperature, and ii) increases with increasing PUFA. These trends suggest that Daphnia compensate for thermal stress by actively remodelling the relative proportions of PUFAs in their membranes.

The authors found that relative proportions of double-bonds and a-linolenic acid decreased with acclimation temperature. Interestingly though, the authors found increased relative EPA abundance in both the warm and cold rearing temperatures.

Based on membrane remodelling under thermal stress, the authors expected to see increased EPA in the cold-reared treatment, but the increased abundance of EPA in the warm-reared treatment is puzzling. However, whether measured EPA represents membrane constituents, as opposed to stored lipids, cannot be determined by the fluorescence polarization methods used here.  Thus, while there is some evidence of PUFA remodelling in response to rearing temperature, Daphnia membrane fluidity and thereby heat tolerance appear to be compromised by high uptake of EPA in warm rearing conditions.


Why I chose this paper

Many human diseases are thought to result from mismatches between developmental conditions and future environments. I chose this paper because nutritional development represents an increasingly important and rapidly growing field in biomedical research. There is relatively less, but growing interest in the role developmental nutrition plays in mediating ecological processes at an individual- and population level. While the findings of this work may be difficult to interpret in respect to ‘general rules’, the authors clearly show that thermal and dietary developmental conditions have lasting effects on subsequent ecological traits, namely thermal tolerance.


What next?

Important avenues for future research would include directly determining the relative amounts of EPA incorporation into plasma membranes across developmental temperatures, possibly via sub fractioning whole-animal extracts. How would it change the interpretation of these findings if elevated EPA in the warm treatment is attributed to lipid storage, rather than membrane lipids?



 Sinensky, M., 1974. Homeoviscous adaptation—a homeostatic process that regulates the viscosity of membrane lipids in Escherichia coli. Proceedings of the National Academy of Sciences71(2), pp.522-525.

Tags: daphnia, development, diet, epa, fluidity, membrane, nutrition, plasticity, pufa, stress, temperature, thermal tolerance

Posted on: 20th May 2018 , updated on: 21st May 2018

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