Document Detail

Oxygen hypothesis of polar gigantism not supported by performance of Antarctic pycnogonids in hypoxia.
MedLine Citation:
PMID:  19129117     Owner:  NLM     Status:  MEDLINE    
Compared to temperate and tropical relatives, some high-latitude marine species are large-bodied, a phenomenon known as polar gigantism. A leading hypothesis on the physiological basis of gigantism posits that, in polar water, high oxygen availability coupled to low metabolic rates relieves constraints on oxygen transport and allows the evolution of large body size. Here, we test the oxygen hypothesis using Antarctic pycnogonids, which have been evolving in very cold conditions (-1.8-0 degrees C) for several million years and contain spectacular examples of gigantism. Pycnogonids from 12 species, spanning three orders of magnitude in body mass, were collected from McMurdo Sound, Antarctica. Individual sea spiders were forced into activity and their performance was measured at different experimental levels of dissolved oxygen (DO). The oxygen hypothesis predicts that, all else being equal, large pycnogonids should perform disproportionately poorly in hypoxia, an outcome that would appear as a statistically significant interaction between body size and oxygen level. In fact, although we found large effects of DO on performance, and substantial interspecific variability in oxygen sensitivity, there was no evidence for sizexDO interactions. These data do not support the oxygen hypothesis of Antarctic pycnogonid gigantism and suggest that explanations must be sought in other ecological or evolutionary processes.
H Arthur Woods; Amy L Moran; Claudia P Arango; Lindy Mullen; Chris Shields
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Proceedings. Biological sciences / The Royal Society     Volume:  276     ISSN:  0962-8452     ISO Abbreviation:  Proc. Biol. Sci.     Publication Date:  2009 Mar 
Date Detail:
Created Date:  2009-02-09     Completed Date:  2009-03-24     Revised Date:  2013-06-02    
Medline Journal Info:
Nlm Unique ID:  101245157     Medline TA:  Proc Biol Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  1069-75     Citation Subset:  IM    
Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
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MeSH Terms
Antarctic Regions
Arthropods / anatomy & histology,  physiology*
Body Weight
Oceans and Seas
Oxygen Consumption / physiology*

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