Morpho-physiological analyses of critical developmental windows of the cardiorespiratory system of tadpoles

• Grant number: 18/04707-5
• Support Opportunities: Regular Research Grants
• Duration: October 01, 2018 - March 31, 2021
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Wilfried Klein
• Grantee: Wilfried Klein
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Temporary ponds may present large physico-chemical variations, such as temperature, pH and dissolved oxygen. Several anuran species deposit their eggs in temporary aquatic ponds maintained exclusively by rain. Additionally to the physico-chemical variations in the pond, tadpoles are also subject to dehydration, hypoxia or even anoxia during periods of drought. During larval development in anurans respiration can be bimodal, either (internal or external) gills serving aquatic gas exchange, or lungs serving air breathing. The pulmonary development, just as lung size and functionality, however, are significantly influenced by environmental parameters such as temperature, water or oxygen availability. Taking into account physic-chemical fluctuations in temporary ponds and the developmental plasticity seen in anurans, we ask the following questions: Does larval anuran development possess a critical window that allows pulmonary respiration to develop earlier or later during ontogeny as a response to environmental stressors? If so, does this critical window vary between different stressors and species? If lung development is anticipated, are the lungs functional? These questions are important to understand how the investigated species develop in their natural habitat and the plasticity in chronological developmental alterations of certain structures. Furthermore, future research will be able to study developmental plasticity of structures important for a species' survival in a more comparative way. The present study has the objective to analyze and describe the development of the larval anuran respiratory system, its morphology (stereology) and function (respirometry), in two species under conditions of hypoxia and hydric stress. We hypothesize that species reproducing in temporary ponds could anticipate larval lung development in conditions of hypoxia and dehydration when compared to tadpoles developing in normoxia and no dehydration stress. We therefore suggest a short window of aquatic respiration and the anticipation of development of functional lungs in these species. (AU)