| Grant number: | 11/22537-0 |
| Support Opportunities: | Regular Research Grants |
| Start date: | March 01, 2012 |
| End date: | August 31, 2014 |
| Field of knowledge: | Biological Sciences - Physiology - Compared Physiology |
| Principal Investigator: | John Campbell McNamara |
| Grantee: | John Campbell McNamara |
| Host Institution: | Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil |
| Associated researchers: | Carolina Arruda de Oliveira Freire ; Luciana Rodrigues de Souza Bastos ; Rogério Oliveira Faleiros |
Abstract
Abiotic environmental parameters like temperature, pO2 and pCO2, pH, water availability and salinity often vary daily, seasonally and/or latitudinally to different degrees. Homeostasis at the organismal level underpins the occupation of habitats characterized both by cyclic alterations in these parameters and by the extreme values attained, as seen in intertidal zones, estuaries and rocky coasts, from the tropics to temperate and sub-polar regions. The physiological mechanisms underlying such organismal homeostasis act at all levels of biological organization, from the subcellular to the systemic, and include processes characteristic of each structural level such as alterations in respiratory metabolism, intracellular isosmotic and extracellular anisosmotic regulation, and alterations in the expression of transport and thermal shock proteins. The present investigation will evaluate at the systemic, biochemical and molecular levels, the thermal, metabolic and osmoregulatory processes that sustain homeostasis in a eubrachyuran crab clade, aiming to appreciate the evolutionary physiology underpinning the diversification of this group into distinct thermal and osmotic niches. The species to be used pertain to four typical intertidal crab families that exhibit a vertical distribution between the low and high tide marks, and a tropical to sub-polar latitudinal distribution. In the laboratory, the crabs will be subjected to controlled conditions of temperature and salinity, and various level-specific biological parameters will be measured: mass-specific oxygen consumption and carbon dioxide production; kinetic (Km) and catalytic properties (kcat) of the enzyme LDH in muscle and gill, in addition to LDH mRNA expression; activity and mRNA expression of the gill ion transporters Na+/K+- and V(H+)-ATPase, and expression of the gill Na+/K+/2Cl- symporter; and mRNA expression and quantification of the thermal shock protein hsp70. The data will be evaluated using comparative phylogenetic methods, focusing on the physiological transformations that have arisen during the evolution of the Eubrachyura and on the macroevolutionary implications of thermal, metabolic and osmotic homeostasis regarding the diversification of habitats occupied by this taxon. (AU)
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