Corticosterone treatment results in fat deposition and body mass maintenance without effects on feeding behaviour or immunity in female lizards (Tropidurus catalanensis)

In different life history stages, animals must maintain homeostasis through predictable, unpredictable and/or challenging events. Glucocorticoids (GC), hormones released in response to hypothalamus-pituitary-adrenal/interrenal (HPA/HPI) axis activation, promote various behavioural and physiological adjustments on a daily manner; and in order to restore balance, after facing stressors. When GC are elevated for an extended period and in high concentrations, characterizing a chronic exposure, it can lead to deleterious effects on animals’ physiology, such as accumulation of fat bodies, changes in feeding behaviour and suppression of immune function. We aim to elucidate the effects of chronic corticosterone exposure and body condition index (BI) in fat deposition, feeding behaviour and immune function in Tropidurus catalanensis’ females. Thirty animals were divided in three groups: 1. Control (no experimental procedure was performed); 2. Empty Implant (animals surgically received an empty silastic tube); and 3. CORT Implant (animals surgically received one silastic tube filled with CORT). Blood samples were collected throughout the experiment to assess CORT plasma levels, total and differential leukocyte count, bacterial killing ability (BKA), and hemagglutination titer. An immune challenge using phytohemagglutinin (PHA) was conducted to measure innate and adaptive immune response. Feeding behaviour and fat bodies were also evaluated. After implantation, CORT treated animals maintained a stable body mass through weeks of captivity, while Control and Empty Implant groups displayed weight loss. In the CORT treated animals, there was also a positive relation between BI and fat bodies, and higher fat bodies deposition when compared to groups 1 and 2. No effects of CORT treatment were observed on immune response or feeding behaviour.