Leukocyte profiles of two neotropical anuran species affected by anthropogenic habitat alteration

Many amphibian species are vulnerable to environmental changes, especially in the tropics where presumably a large number of species have evolved narrow niches. Rapid environmental changes, such as deforestation, may promote stress responses in anurans that could affect population viability. The stress response in vertebrates is highly conserved, often involving the liberation of glucocorticoids hormones and the recruitment of immune competent cells. The objective of this work was to evaluate leukocyte profiles among individuals of two neotropical anuran species affected by anthropogenic habitat alteration. We took blood samples from adult individuals of Physalaemus cuvieri and Scinax x-signatus in natural and converted habitats in NE Brazil. We analyzed differential leukocyte counts, where increases in neutrophils and decreases in lymphocytes are indicative of a stress response. Specimens of S. x-signatus captured in highly altered habitats presented a higher neutrophil:lymphocyte (N:L) ratios than individuals from natural habitats. In contrast, P. cuvieri individuals exhibited no difference in N:L ratios between habitat types. These results suggest that the immune response depends on the species and the level of habitat alteration. Although S. x-signatus can be considered a generalist species, individuals from this species exhibited increased stress response associated with habitat alteration. The lack of a strong stress response of P. cuvieri, may suggest that this species is more tolerant of habitat alteration or that those individuals have acclimated to anthropogenic stressors more rapidly than S. x-signatus. These variable responses of immune function in highly altered habitats suggest avenues for future experimental work that examines responses to multiple stressors, including disease, which could scale to population trends in altered habitats.