Does geographic variation in thermal tolerance in Daphnia represent trade-offs or conditional neutrality?

Geographic variation in thermal tolerance in Daphnia seems to represent genetic load at the loci specifically responsible for heat tolerance resulting from conditional neutrality. We see no evidence of trade-offs between fitness-related traits at 25 °C vs. 10 °C or between two algal diets across Daphnia magna clones from a variety of locations representing the opposite ends of the distribution of long-term heat tolerance.

Breaking free from thermodynamic constraints: thermal acclimation and metabolic compensation in a freshwater zooplankton species.

Respiration rates of ectothermic organisms are affected by environmental temperatures, and sustainable metabolism at high temperatures sometimes limits heat tolerance. Organisms are hypothesized to exhibit acclimatory metabolic compensation effects, decelerating their metabolic processes below Arrhenius expectations based on temperature alone. We tested the hypothesis that either heritable or plastic heat tolerance differences can be explained by metabolic compensation in the eurythermal freshwater zooplankton crustacean We measured respiration rates in a ramp-up experiment over a range of assay temperatures (5-37°C) in eight genotypes of representing a range of previously reported acute heat tolerances and, at a narrower range of temperatures (10-35°C), in with different acclimation history (either 10 or 25°C).

Rearing Temperature and Fatty Acid Supplementation Jointly Affect Lipid Fluorescence Polarization and Heat Tolerance in .

The homeoviscous adaptation hypothesis states that the relative abundance of polyunsaturated fatty acids (PUFAs) in membrane phospholipids of ectothermic organisms decreases with increasing temperatures to maintain vital membrane properties. We reared at 15°, 20°, and 25°C and increasing dietary concentrations of the long-chain PUFA eicosapentaenoic acid (EPA) to test the hypothesis that the well-documented increase in heat tolerance of high-temperature-reared is due to a reduction in body PUFA concentrations. Heat tolerance was assessed by measuring the time to immobility at a lethally high temperature ( at 37°C), and whole body lipid fluorescence polarization (FP) was used as an estimate of membrane fluidity.

Antioxidant capacity, lipid peroxidation, and lipid composition changes during long-term and short-term thermal acclimation in Daphnia.

Examples of phenotypic plasticity-the ability of organisms of identical genotypes to produce different phenotypes in response to the environment-are abundant, but often lack data on the causative physiology and biochemistry. Phenotypes associated with increased protection against or reduced damage from harmful environments may, in fact, be downstream effects of hidden adaptive responses that remain elusive to experimental measurement or be obscured by homeostatic or over-compensatory effects. The freshwater zooplankton crustacean Daphnia drastically increases its heat tolerance as the result of acclimation to high temperatures, an effect often assumed to be based on plastic responses allowing better protection against oxidative stress.

Unbiased measurements of reconstruction fidelity of sparsely sampled magnetic resonance spectra.

The application of sparse-sampling techniques to NMR data acquisition would benefit from reliable quality measurements for reconstructed spectra. We introduce a pair of noise-normalized measurements, and , for differentiating inadequate modelling from overfitting. While and can be used jointly for methods that do not enforce exact agreement between the back-calculated time domain and the original sparse data, the cross-validation measure is applicable to all reconstruction algorithms.