Document Detail

Respiratory and acid-base responses during migration and to exercise by the terrestrial crab Discoplax (Cardisoma) hirtipes, with regard to season, humidity and behaviour.
MedLine Citation:
PMID:  16272255     Owner:  NLM     Status:  MEDLINE    
The terrestrial crab Discoplax hirtipes (formerly Cardisoma hirtipes) exhibits a seasonally dichotomous activity pattern governed by the seasonal rainfall on Christmas Island, with a breeding migration in the wet season. Greater activity in the wet season reflects a release of constraints on ion and water balance independent of changes in exercise physiology. The respiratory responses to walking exercise by D. hirtipes were assessed with regard to humidity and season. In the laboratory, crabs walked 38% faster when humidity was high, while the O(2) uptake across the lung became diffusion limited despite a Ca(2+)-induced increase in O(2) affinity of the haemocyanin. Crabs walking in 90% relative humidity exhibited a larger metabolic acidosis while re-oxidation of l-lactate was only 0.49 mmol l(-1) h(-1). The wet-season crabs were more active and exhibited a respiratory acidosis compared with the quiescent dry-season crabs. The migration was close to the limit of the aerobic scope of the crabs, and the pulmonary oxygen partial pressure (P(O(2))) was depressed, the O(2) uptake diffusion limited and the arterial-venous P(O(2)) difference diminished. Additional, enforced exercise induced a metabolic acidosis. The optimum strategy for migration would be walking continuously but at a speed within the aerobic scope. D. hirtipes is influenced by seasonal rain and responds to lower ambient humidity by limiting exercise. The behavioural response is paramount since the changes in respiratory status were determined primarily by the differences in commitment to, and investment in, walking and not by direct effects of humidity on respiratory physiology.
Steve Morris
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  The Journal of experimental biology     Volume:  208     ISSN:  0022-0949     ISO Abbreviation:  J. Exp. Biol.     Publication Date:  2005 Nov 
Date Detail:
Created Date:  2005-11-07     Completed Date:  2006-06-20     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0243705     Medline TA:  J Exp Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  4333-43     Citation Subset:  IM    
Integrative and Environmental Physiology, School of Biological Sciences, University of Bristol, UK.
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MeSH Terms
Analysis of Variance
Animal Migration*
Blood Glucose
Brachyura / physiology*
Calcium / metabolism
Hemocyanin / metabolism
Hemolymph / metabolism
Hydrogen-Ion Concentration
Lactic Acid / blood
Locomotion / physiology*
Muscles / metabolism
Osmolar Concentration
Oxygen / blood,  metabolism
Oxygen Consumption / physiology
Partial Pressure
Physical Exertion / physiology*
Uric Acid / metabolism
Reg. No./Substance:
0/Blood Glucose; 50-21-5/Lactic Acid; 69-93-2/Uric Acid; 7440-70-2/Calcium; 7782-44-7/Oxygen; 9013-72-3/Hemocyanin

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

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