Is resting metabolic rate related to reproductive output in an orb-web spider, Argiope radon?

1. Resting metabolic rate (RMR) is a fundamental feature of animal biology that reflects the baseline level of energy expenditure. There are two main strategies that can address energy demands; animals can reallocate energy from maintenance by reducing RMR to meet energy demands (compensation model) or they can increase intake rate by increasing metabolic activities (performance model). 

2. Orb-web spiders are sit-and-wait foragers that typically reside at the centre of their web waiting to intercept prey. Given their sedentary resource acquisition strategy, it is predicted that lower RMR is favoured to reduce self-maintenance energetic costs and to allow greater allocation to oogenesis (i.e., egg sac development). 

3. In this study, we tested temporal variation in RMR of female Argiope radon (Araneae: Araneidae) spiders in response to mating status. Then we tested the degree to which between-individual variation in the parental RMR relates to reproductive output and spiderling early life-history traits. 

4. Despite the notable between-individual variation, we found a temporal consistency of RMR in the female spiders at early adulthood. Mated females significantly reduced their RMR by around 35% compared to their unmated stage which supports compensation model. However, there was a significant correlation between female RMR and mass of the egg sac in these spiders which is an evidence for performance model. 

5. Our findings suggest that energy management in this species is a complex phenomenon, both strategies are in effect simultaneously at within- and between-individual level shaping the individuals' phenotype.