| Insects breathe discontinuously to avoid oxygen toxicity. | |
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MedLine Citation:
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PMID: 15690040 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The respiratory organs of terrestrial insects consist of tracheal tubes with external spiracular valves that control gas exchange. Despite their relatively high metabolic rate, many insects have highly discontinuous patterns of gas exchange, including long periods when the spiracles are fully closed. Two explanations have previously been put forward to explain this behaviour: first, that this pattern serves to reduce respiratory water loss, and second, that the pattern may have initially evolved in underground insects as a way of dealing with hypoxic or hypercapnic conditions. Here we propose a third possible explanation based on the idea that oxygen is necessary for oxidative metabolism but also acts as a toxic chemical that can cause oxidative damage of tissues even at relatively low concentrations. At physiologically normal partial pressures of CO2, the rate of CO2 diffusion out of the insect respiratory system is slower than the rate of O2 entry; this leads to a build-up of intratracheal CO2. The spiracles must therefore be opened at intervals to rid the insect of accumulated CO2, a process that exposes the tissues to dangerously high levels of O2. We suggest that the cyclical pattern of open and closed spiracles observed in resting insects is a necessary consequence of the need to rid the respiratory system of accumulated CO2, followed by the need to reduce oxygen toxicity. |
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Authors:
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Stefan K Hetz; Timothy J Bradley |
Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Nature Volume: 433 ISSN: 1476-4687 ISO Abbreviation: Nature Publication Date: 2005 Feb |
Date Detail:
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Created Date: 2005-02-03 Completed Date: 2005-02-23 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0410462 Medline TA: Nature Country: England |
Other Details:
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Languages: eng Pagination: 516-9 Citation Subset: IM |
Affiliation:
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Department of Animal Physiology, Humboldt-Universität zu Berlin, Philippstr. 13, 10115 Berlin, Germany. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Basal Metabolism / physiology Carbon Dioxide / metabolism Diffusion Hydrostatic Pressure Insects / anatomy & histology, drug effects*, physiology* Models, Biological* Oxidative Stress / drug effects Oxygen / metabolism*, toxicity* Pulmonary Gas Exchange / physiology Respiration* Respiratory System / anatomy & histology, metabolism Time Factors |
| Chemical | |
Reg. No./Substance:
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124-38-9/Carbon Dioxide; 7782-44-7/Oxygen |
| Comments/Corrections | |
Comment In:
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Nature. 2005 Feb 3;433(7025):471-2
[PMID:
15690026
]
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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