Seasonal physiology in the tegu lizard Salvator merianae: an animal model for assessing physiological functions in a dynamic and changing environment

• Grant number: 17/01652-2
• Support Opportunities: Scholarships in Brazil - Post-Doctorate
• Effective date (Start): September 01, 2017
• Effective date (End): January 31, 2021
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Carlos Arturo Navas Iannini
• Grantee: Lucas Aparecido Zena
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 14/16320-7 - Impacts of climate/environmental change on the fauna: an integrative approach, AP.PFPMCG.TEM
• Associated scholarship(s): 19/12311-7 - Physiological plasticity and consequences of global change in ectothermic organisms, BE.EP.PD 18/06192-2 - Seasonal physiology in the tegu lizard Salvator merianae: an animal model for assessing physiological functions in a dynamic and changing environment, BE.EP.PD

Abstract

The South American tegu lizard, Salvator merianae, has annual cycles of high activity during the spring and summer and hibernation during winter, a seasonal rhythm that is independent of ambient temperature (Ta). Furthermore, during the breeding season in spring, animals are able to maintain core body temperature (Tb) above Ta using increased endogenous heat production, making S. merianae the only known facultative endothermic lizard. S. merianae is, therefore, a unique platform to investigate mechanisms of seasonal variation in behavior and physiology and to generate insights for the evolution of endothermy. In this context, the mechanisms involved in endogenous seasonal changes are not yet known. The first candidates we propose to investigate are the hormones known to be involved in energy metabolism (thyroid hormones) and reproduction (gonadal steroids). Thus, the aim of this project is to evaluate the interrelationships of seasonal changes in T3, T4, TSH, testosterone and estradiol with seasonal changes in activity levels and body temperature of S. merianae in the same individual over a year. Knowledge of the physiological adjustments in a seasonal environments is relevant for understanding how a specie may adjust their phenotype to short-term environmental fluctuations, such as a real-world problem as the magnitude of climate change. We hypothesize that endocrine changes will precede the observed behavioral and metabolic changes and predict that reduced plasma thyroid hormone concentrations will be associated with decreased motor activity during hibernation, independent of Tb, and increased concentrations of thyroid and sex hormones will precede the post-hibernation increases in motor activity, thermogenesis and reproduction. To test this hypothesis, each adult animal (males and females) will be marked with a subcutaneous microchip, implanted with a temperature logger into the coelomic cavity for semicontinuous measurements of core Tb (each 70 mins) and will be affixed with an accelerometer for three-dimensional measurements of movement (1 Hz). Devices will be deployed for an entire year; blood samples will be collected monthly for later analysis of hormone concentrations. The animals will be kept in a semi-natural habitat under the influence of natural changes in temperature and photoperiod.

Scientific publications

(5)

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

ZENA, LUCAS A.; DILLON, DANIELLE; HUNT, KATHLEEN E.; NAVAS, CARLOS A.; BICEGO, KENIA C.; BUCK, C. LOREN. Seasonal changes in plasma concentrations of the thyroid, glucocorticoid and reproductive hormones in the tegu lizard Salvator merianae. General and Comparative Endocrinology, v. 273, n. SI, p. 134-143, MAR 1 2019. (17/01652-2, 15/04849-6, 14/16320-7)

ZENA, LUCAS A.; DILLON, DANIELLE; HUNT, KATHLEEN E.; NAVAS, CARLOS A.; BUCK, C. LOREN; BICEGO, KENIA C.. Hormonal correlates of the annual cycle of activity and body temperature in the South-American tegu lizard (Salvator merianae). General and Comparative Endocrinology, v. 285, JAN 1 2020. (15/04849-6, 18/06192-2, 14/16320-7, 17/01652-2)

ZENA, LUCAS A.; EKSTROM, ANDREAS; GRANS, ALBIN; OLSSON, CATHARINA; AXELSSON, MICHAEL; SUNDH, HENRIK; SANDBLOM, ERIK. t takes time to heal a broken heart: ventricular plasticity improves heart performance after myocardial infarction in rainbow trout, Oncorhynchus mykis. Journal of Experimental Biology, v. 224, n. 23, DEC 2021. (17/01652-2, 19/12311-7)

MADELAIRE, CARLA B.; ZENA, LUCAS A.; DILLON, DANIELLE; SILVA, DIEGO P.; HUNT, KATHLEEN E.; BUCK, C. LOREN; BICEGO, KENIA C.; GOMES, FERNANDO R.. ho Rules Over Immunology? Seasonal Variation in Body Temperature, Steroid Hormones, and Immune Variables in a Tegu Lizar. INTEGRATIVE AND COMPARATIVE BIOLOGY, v. 61, n. 5, p. 1867-1880, NOV 2021. (12/24206-4, 18/00406-0, 15/04849-6, 14/16320-7, 19/13164-8, 17/01652-2)

ZENA, LUCAS A.; DILLON, DANIELLE; HUNT, KATHLEEN E.; NAVAS, CARLOS A.; BICEGO, KENIA C.; BUCK, C. LOREN. easonal changes in steroid and thyroid hormone content in shed skins of the tegu lizard Salvator meriana. JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL, v. 192, n. 1, AUG 2021. (14/16320-7, 17/01652-2, 18/06192-2, 15/04849-6)