The standard metabolic rate of a land snail (Cepaea hortensis) is a repeatable trait and influences winter survival.

Phenotypic selection on physiological parameters is an underrepresented topic in studies of evolutionary biology. There is especially a lack of studies involving invertebrate organisms. We studied the repeatability of the standard metabolic rate (SMR) and the effect of individual variation in SMR on the subsequent winter survival in a terrestrial shell-bearing mollusc, the white-lipped snail (Cepaea hortensis) in mid-Norway. SMR was measured twice during the autumn and - after an experimental overwintering at controlled conditions - twice during the following spring. We found a significant repeatability of SMR over all three time periods tested, with a clear effect of time, with a high repeatability of 0.56 over 4 days during spring, 0.44 over 12 days in the autumn and 0.17 over 194 days from autumn to spring. That SMR is a repeatable physiological trait across the winter period during which a possible selection might occur, suggests that SMR could be a potential target of natural selection. We indeed found that the autumn SMR significantly influenced the probability of survival during the winter period, with a combination of a positive linear (P = .011) and a quadratic stabilizing (P = .001) effect on SMR. Our results hence support the view that metabolic rate is an important physiological component influencing the fitness of an organism.

Metabolic rate and muscle activation level when wearing state-of-the-art cold-weather protective clothing during level and inclined walking.

Use of cold-weather personal protective clothing (PPC) in cold climates is essential but can add metabolic cost to the wearer. This study measured the effect of wearing state-of-the-art PPC and personal protective equipment (PPE), with the possible effect of clothing layers and fit, on physiological responses including metabolic rate (MR) and muscle activation level. 19 male participants (80.2 ±â€¯5.9 kg, 181.5 ±â€¯5.1 cm) wore five different clothing ensembles during level (0°) and inclined (6°) walking. Compared to a base layer ensemble (388.7 ±â€¯42.7 W/737.8 ±â€¯57.9 W), wearing a 3-layer PPC ensemble (421.5 ±â€¯44.7 W/811.7 ±â€¯69.2 W) significantly increased MR, and adding PPE (458.3 ±â€¯59.8 W/864.5 ±â€¯71.2 W) further increased MR during level/inclined walking. Independent of the extra weight, adding a middle layer between base layer and outer clothing significantly increased MR during inclined walking only, and no effect of oversized outer clothing was measured.