Relationships between hormone levels and life-history phases in squamates

• Grant number: 21/10877-3
• Support Opportunities: Regular Research Grants
• Duration: August 01, 2022 - July 31, 2024
• Field of knowledge: Biological Sciences - Zoology - Physiology of Recent Groups
• Principal Investigator: Fernando Ribeiro Gomes
• Grantee: Fernando Ribeiro Gomes
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Carla Bonetti Madelaire ; Charles Loren Buck ; Erika Hingst-Zaher

Abstract

Hormones display broad effects in different aspects of vertebrates' phenotypes, physiologically mediating transitions between life-history phases. Vertebrates that display seasonal reproduction or go through marked changes during development, for example, show clear and well-marked variations in hormone levels. Although endocrine mediation of metamorphosis has been well investigated, less dramatic phenotypic changes occurring across ontogeny of ectothermic vertebrates are still virtually unexplored. Many Viperidae snakes, for example, are known to undergo complex phenotypic shifts during ontogeny, including prey preference, micro-habitat use, the presence of caudal luring in young individuals and changes in venom composition. It is highly probable that such phenotypic changes during ontogeny of viperid snakes are mediated by hormones. Interestingly, the exposure of females to adverse environmental conditions can cause neuroendocrine and physiological changes in the offspring, when juveniles and even adults. These transgenerational effects are mediated by epigenetic mechanisms, including the transference of steroid hormones to the egg yolk during vitellogenesis. Physiological consequences of maternal stress on the physiological state of offspring have been also poorly investigated, particularly regarding immune function. We propose two independent subprojects on the relationship between hormones and aspects of life-history and ontogeny of squamates, to be conducted by two Master's students, and both projects will be assisted by national and international collaborators. One of them propose to study the effects of chronically high corticosterone on reproductive physiology and immunity of gravid females of western collared spiny lizards (Tropidurus catalanensis), as well as the body condition and immune function of their offspring. The second project will investigate temporal dynamics of hormone plasma levels and phenotypic changes throughout the ontogeny of the jararaca pitviper (Bothrops jararaca). (AU)