Effects of extreme temperature events and increases in mean temperature on the leukocyte profile in frogs (Rhinella diptycha)

• Grant number: 25/00623-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2025
• End date: December 31, 2025
• Field of knowledge: Biological Sciences - Physiology - General Physiology
• Principal Investigator: Fernando Ribeiro Gomes
• Grantee: Lucas Máximo de Oliveira Moreira
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Anthropogenic climate changes are leading to an increase in the global mean temperature and a higher incidence of extreme climate events, impairing the physiology of animals, with highlights for their effects on the immunity, given that these conditions act as stressors capable of interfering with the corticosterone (CORT) secretion and the leukocytes profile. Furthermore, the repetitive (or prolonged) exposure to stressors may dampen the organism's capacity to properly respond to subsequent stressors as the pathogen infection. Considering different effects of stress on the immune response in Anurans, we can hypothesize that cururu toads (Rhinella diptycha) exposed to an extreme climate event (E) will show exacerbated responses to an immune challenge comparing those exposed to an increase in the mean temperature (M) or the control group (C), and the "E group" will present an extent of response to a subsequent stressor (the immune challenge) similar to the "C group" and higher than the "M group", allowing to say that, after the exposure to different thermal regimes, the "E group" will present a neutrophil:lymphocyte ratio (NLR) and CORT higher than both the groups C and M, and after the second stressor, the "E group" will show similar values of these parameters comparing with the "C group", meanwhile the "M group" will present lower values. For this purpose, the NLR and the circulating CORT will be analyzed from animals previously collected and exposed to different thermal regimes, with or without a second stressor, an immune challenge.