Document Detail


Insects breathe discontinuously to avoid oxygen toxicity.
MedLine Citation:
PMID:  15690040     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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.
Authors:
Stefan K Hetz; Timothy J Bradley
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Nature     Volume:  433     ISSN:  1476-4687     ISO Abbreviation:  Nature     Publication Date:  2005 Feb 
Date Detail:
Created Date:  2005-02-03     Completed Date:  2005-02-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  516-9     Citation Subset:  IM    
Affiliation:
Department of Animal Physiology, Humboldt-Universität zu Berlin, Philippstr. 13, 10115 Berlin, Germany.
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MeSH Terms
Descriptor/Qualifier:
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:
124-38-9/Carbon Dioxide; 7782-44-7/Oxygen
Comments/Corrections
Comment In:
Nature. 2005 Feb 3;433(7025):471-2   [PMID:  15690026 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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