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Adaptive thermogenesis in hummingbirds.
José Eduardo P W Bicudo1, Antonio C Bianco, Cláudia R Vianna
1Department of Physiology, Biosciences Institute, University of São Paulo, SP, Brazil. jebicudo@usp.br
The Journal of Experimental Biology
|July 12, 2002
Summary
Birds can generate heat without shivering, challenging previous assumptions. Skeletal muscles, particularly flight muscles, are now identified as key sites for this non-shivering thermogenesis in avian species.
Area of Science:
- Physiology
- Animal Biology
- Thermoregulation
Background:
- Birds, as endotherms, share a common ancestor with mammals but lack brown adipose tissue.
- Despite this, some bird species exhibit remarkable cold tolerance and heterothermia.
- Evidence suggests non-shivering thermogenesis occurs in birds, particularly under extreme conditions.
Purpose of the Study:
- To investigate the mechanisms of non-shivering thermogenesis in birds.
- To identify the primary sites of heat production in avian species.
- To explore the role of specific proteins in avian thermoregulation.
Main Methods:
- Analysis of skeletal muscle function in thermoregulation.
- Investigating calcium (Ca2+) translocation via sarcoplasmic reticulum Ca2+-ATPase.
- Characterizing uncoupling protein homologs and mRNA expression in avian skeletal muscle.
Main Results:
- Avian skeletal muscles, especially flight muscles, are major sites of non-shivering thermogenesis.
- Calcium cycling in muscle cells is a proposed mechanism for heat generation.
- An uncoupling protein homolog in avian muscle suggests a role in thermogenesis, particularly during rewarming.
Conclusions:
- Non-shivering thermogenesis in birds is primarily mediated by skeletal muscles.
- Sarcoplasmic reticulum Ca2+-ATPase activity and uncoupling proteins are potential contributors to avian heat production.
- Further research is needed to fully elucidate the complex mechanisms of adaptive thermogenesis in birds.