Meeting Abstract
Maximal thermogenic capacity (Msum) in wild black-capped chickadees suggests that phenotypic adjustments are slow and begin to take place before winter peaks. However, when mean minimal Ta reaches -10°C, birds’ phenotype appears to provide enough reserve capacity in cold endurance to buffer days with Ta of -20°C or below. This would imply that reserve capacity could also affect other systems. For example, birds could maintain a higher antioxidant capacity as part of their cold acclimated phenotype. In terms of oxidative stress, this may mean that RS (reactive species) production associated with increases in metabolic rate for thermogenesis would remain below antioxidant capacity in cold-acclimated birds to avoid damage during periods of high metabolic rate. Here, we tested how environmental mismatch affected oxidative stress by comparing variation of specific parameters in cold acclimated (-5°C) black-capped chickadees exposed to a 15°C drop in temperature (treatment; -5°C to -20°C) to that of control individuals (remaining at -5°C). We measured sodium dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, as well as lipid peroxidation (LPO) damage, and antioxidant scavenging capacity in pectoralis muscle, brain, intestine and liver. We found that SOD, CAT and GPx varied with regards to tissue type. LPO did not differ by treatment, tissue or treatment*tissue. Peroxyl varied with regards to tissue type. Hydroxyl varied with regards to tissue and treatment*tissue. Control liver hydroxyl values were marginally higher than treatment liver values and control muscle hydroxyl values were lower than treatment muscle values. The increase in OH scavenging capacity during cold shock in muscle could be related to an increase in food intake.
