Professor East Tennessee State University Johnson City, Tennessee, United States
Background/Question/Methods
Dietary available essential fatty acid content can affect organisms’ abilities to tolerate stress and even lifespan. We analyzed life histories and heat tolerance in four genotypes of Daphnia reared on two diets, green alga Scenedesmus and heterokont alga Nannochloropsis, which are, respectively, poor and rich in long chain ω-3 polyunsaturated fatty acids.
Results/Conclusions
We observed a significant genotype-by-diet interaction in lifespan: Nannochloropsis diet expanded lifespan of otherwise short-lived genotypes, but not of long-lived ones. Acute heat tolerance was slightly lower overall on Scenedesmus diet, than on Nannochloropsis diet and under full diet than under limited diet. Daphnia on the Nannochloropsis diet showed lower mitochondrial membrane potential (ΔΨm), but also, surprisingly, a reduced level of lipid peroxidation (LPO). LPO levels were inversely related to acute heat tolerance, consistently with dietary and clonal differences. In contrast, Daphnia with intermediate levels of ΔΨm appeared to demonstrate the lowest heat tolerance. Neither LPO nor ΔΨm explained the dietary effects on lifespan. We hypothesize that PUFA-rich diet contains antioxidants that reduce LPO and directly or indirectly affect heat tolerance, and may also be responsible for the expansion of lifespan of short-lived genotypes.
