Meeting Abstract
To understand how stress and immunity in cane toads (Rhinella marina) changes throughout the dispersal range in Florida, we measured stress (corticosterone levels [CORT] and neutrophil lymphocyte ratio [NL]) and innate immune parameters (bacterial killing ability [BKA] and natural antibody titers [Ab]) before and after submitting them to a restraint challenge (1h in a plastic bag). When comparing Southern and Northern populations, there were no differences in baseline CORT, NL, or Ab, but BKA was significantly higher in Southern populations (F1,77=16.8; p≤0.001). After restraint, CORT (F1,67=9.3; p=0.003) and Ab (F1,66=9.8, p=0.003) differed, with Southern populations exhibiting higher values than Northern ones for both measures. In addition, we calculated the magnitudes of change for each variable and compared between the regions. After the restraint, individuals from the Southern population exhibited larger CORT response than their Northern counterparts (9 fold vs. 3 fold change; F1,67=5.7; p=0.02). In contrast, NL decreased in Southern toads, while increasing in Northern toads (-13% vs. +26%; F1,62=4.4; p=0.04) after the restraint challenge. Since the CORT response was higher in the South, we are possibly seeing an immunosuppressive effect on leukocyte redistribution. Additionally, the lower CORT response to the restraint in Northern toads, allowed a more robust change in white blood cell dynamics (possibly a immunostimulatory effect). Southern toads exhibited both, higher baseline BKA and higher post restraint Ab response, when compared with Northern toads which suggests these toads might have a constitutively better surveillance system. We are exploring if there is an energetic tradeoff between immune response and locomotion abilities between the individuals in these populations.
