Reduced Food Availability Amplifies Behavioral Depression and Impairs Locomotor Performance After Immune Challenge in Xenopus laevis.

Mounting an immune response and locomotor activity are energetically costly processes that can generate trade-offs affecting energy allocation, muscle performance, and activity patterns. The balance between these demands can be modulated by factors such as food availability and ecological conditions, influencing the ability to mount an immune response and maintenance of locomotor activity. In a previous study, we demonstrated that Xenopus laevis subjected to an immune challenge maintained voluntary movement, indicating that behavioral depression did not occur in these animals, contrary to what is observed in most species. We hypothesized that food availability influenced this response, since the animals were captive and fed ad libitum. Here, we investigated the effects of food restriction on the locomotor activity of X. laevis after an immune challenge induced by lipopolysaccharide (LPS). We evaluated locomotor endurance, jump force, and spontaneous voluntary movement in individuals subjected to a progressive, 30-day, food restriction protocol. These results suggest that food restriction alters the energetic prioritization following immune activation, leading to reduced locomotor output and behavioral activity. Furthermore, the reduction in jump force and locomotor endurance was more pronounced in individuals on restricted diet, indicating a direct impact of energy availability on locomotor capacity. These findings reinforce the idea that resource availability influences the immune and locomotor response in anurans, highlighting how nutritional stress may constrain immune-locomotor trade-offs in amphibians, with potential consequences for survival and fitness in resource-limited habitats.