title: The active metabolic rate predicts a male spider's proximity to females and expected fitness.
abstract: Conspicuous traits, such as weaponry and body size, are often correlated with fitness. By contrast, we understand less about how inconspicuous physiological traits affect fitness. Not only is linking physiology directly to fitness a challenge, but in addition, behavioural studies most often focus on resting or basal metabolic rates, resulting in a poor understanding of how active metabolic rates affect fitness. Here we use the golden orb-web spider (Nephila plumipes), a species for which proximity to a female on the web predicts a male's paternity share, to examine the role of resting and active metabolic rates in fitness. Using a semi-natural experimental set-up, we show that males closer to a female have higher active metabolic rates than males further from females. This higher metabolic activity is paralleled by increased citrate synthase activity, suggesting greater mitochondrial densities. Our results link both higher active metabolic rates and increased citrate synthase activity with fitness. Coupled with the behaviour and life history of N. plumipes, these results provide insight into the evolution of physiological systems.
authors: Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, The University of New South Wales, Sydney, Australia. m.kasumovic@unsw.edu.au
authors: Michael M
authors: MM
authors: Kasumovic
authors: Frank
authors: F
authors: Seebacher
mesh_terms: D000818:Animals; D001315:Australia; D001481:Basal Metabolism; D001522:Behavior, Animal / Q000502:physiology*; D005075:Biological Evolution; D049628:Body Size; D002950:Citrate (si)-Synthase / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D004789:Enzyme Activation; D005260:Female; D056084:Genetic Fitness; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000201:enzymology / Q000502:physiology; D010101:Oxygen Consumption; D013045:Species Specificity; D013112:Spiders / Q000378:metabolism* / Q000502:physiology
chemical_list: D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase