Document Detail

Evolution of complex life cycles in helminth parasites.
MedLine Citation:
PMID:  14523438     Owner:  NLM     Status:  MEDLINE    
The fundamental question of how complex life cycles--where there is typically more than one host-evolve in host--parasite systems remains largely unexplored. We suggest that complex cycles in helminths without penetrative infective stages evolve by two essentially different processes, depending on where in the cycle a new host is inserted. In 'upward incorporation', a new definitive host, typically higher up a food web and which preys on the original definitive host, is added. Advantages to the parasite are avoidance of mortality due to the predator, greater body size at maturity and higher fecundity. The original host typically becomes an intermediate host, in which reproduction is suppressed. In 'downward incorporation', a new intermediate host is added at a lower trophic level; this reduces mortality and facilitates transmission to the original definitive host. These two processes should also apply in helminths with penetrative infective stages, although the mathematical conditions differ.
Geoff A Parker; Jimmy C Chubb; Michael A Ball; Guy N Roberts
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Nature     Volume:  425     ISSN:  1476-4687     ISO Abbreviation:  Nature     Publication Date:  2003 Oct 
Date Detail:
Created Date:  2003-10-02     Completed Date:  2003-10-27     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  480-4     Citation Subset:  IM    
Population and Evolutionary Biology Research Group, School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, UK.
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MeSH Terms
Body Constitution
Helminths / growth & development,  physiology*
Host-Parasite Interactions
Life Cycle Stages*
Parasites / growth & development,  physiology*

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