Influence of hydration status on the metabolic and behavioral changes related of hibernation in the tegu lizard Salvator merianae

• Grant number: 22/13834-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2023
• End date: February 29, 2024
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Kênia Cardoso Bícego
• Grantee: Ane Guadalupe Silva
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil
• Associated research grant: 21/10910-0 - Physiological capacities and resilience facing climate change: exploring the functional dimension in ectothermic vertebrates, AP.TEM

Abstract

Water availability, along with temperature and food availability, are critical factors that significantly affect animal physiology, fitness and survival. These environmental factors constitute selective pressures that act within the limits of the animals' capacities and tolerance, including varying degrees of phenotypic flexibility. Based on these organism-environment interactions, seasonal oscillations of those factors can exert a strong influence on animal activity patterns throughout the annual cycles. In this context, the tegu lizard Salvator merianae, native to South America, has attracted attention for its peculiar seasonal physiological oscillation. This species presents high metabolic and motor activities in spring (reproduction) and summer followed by gradual reductions in autumn until reaching the lowest values in winter, when they are accompanied by voluntary fasting. In the southeast region in Brazil, where there is an abundant distribution of S. merianae, the winter season is characterized by mild reductions in ambient temperature and coincides with the dry phase of the year. So there is a possibility of confusion between hibernation events (metabolic reduction during winter) and estivation (metabolic reduction during dry season). There is a lot of evidence that the reduction of the metabolic rate of S. merianae during winter is independent of the ambient temperature, and there are some indications that it may also be independent of the rainfall reduction at this time of the year. Thus, focusing on the seasonal change in water availability, the present study aims to evaluate the influence of hydration status on metabolic and behavioral reduction patterns of the tegu S. merianae during winter in the southeastern Brazil. For this, monthly plasma osmolality, daily body temperature (intra coelomic cavity biologger), general motor activity (three-dimensional accelerometer), and thermoregulatory behaviors (video images) will be evaluated in hydrated and dehydrated males and females (maximum 8%) during pre-hibernation, hibernation and post-hibernation phases. The times for entry and emergence from hibernation in males and females will also be evaluated.