Stress-induced elemental retention in an ectothermic vertebrate.

Physiological stress responses are energy intensive. Animals can meet their stress-induced energetic demands by altering foraging or selectively retaining ingested nutrients, although the latter is poorly studied. We tested the effects of elevated stress on elemental retention in Psammophilus dorsalis. Adult lizards of both sexes were allotted to either a stressed group (daily constraint) or control group for 10 days. We measured baseline corticosterone, glucose, and triglyceride levels of lizards at the beginning and end of the experiment, as well as the total amounts of carbon and nitrogen retained based on the ingested and egested content during the treatment phase. Both control and stressed groups had higher corticosterone levels at the end of the experiment, with stressed group males showing the greatest increase. Glucose and triglyceride levels were variable. Contrary to expectation, lizards from both treatments retained similar amounts of carbon and nitrogen during the experiment phase. Our results do not show support for changes in elemental retention under stressful conditions, although the stress of captivity itself could have masked the potential effect on elemental retention. Our study highlights the need to test elemental retention as a potential strategy to meet stress-induced energetic demands when foraging opportunities are limited.