Document Detail

Outcrossing hermaphroditic polychaete worms adjust their sex allocation to social conditions.
MedLine Citation:
PMID:  16135129     Owner:  NLM     Status:  MEDLINE    
Sex allocation theory predicts that simultaneous hermaphrodites shift sex allocation facultatively in response to variation in local group size. This study was performed to evaluate the relative investment in each sex function by the simultaneously hermaphroditic polychaete worm Ophryotrocha diadema and to test whether allocation to each sex depends on the number of reproductive competitors. Four experimental groups were set up (in a 2 x 2 factorial design) with small or large group size and with small or large enclosures to control for potential confounding effects of density. We measured the proportion of female and male investment in focal individuals. Results revealed that individuals regulated their reproductive output so that when reproductive competitors were present, the number of female gametes was strongly reduced and the male function increased. In contrast, under monogamy, individuals in small groups produced lower numbers of sperm but had a higher egg output than worms in large groups. Density did not affect sex allocation in our experiment. Our findings provide qualitative support for Local Mate Competition theory, but also show that the pattern of sex allocation specific to this species is more complex than expected by current theory.
M C Lorenzi; G Sella; D Schleicherová; L Ramella
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of evolutionary biology     Volume:  18     ISSN:  1010-061X     ISO Abbreviation:  J. Evol. Biol.     Publication Date:  2005 Sep 
Date Detail:
Created Date:  2005-09-01     Completed Date:  2006-02-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8809954     Medline TA:  J Evol Biol     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  1341-7     Citation Subset:  IM    
Department of Animal and Human Biology, University of Turin, Turin, Italy.
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MeSH Terms
Analysis of Variance
Body Weights and Measures
Ovum / physiology
Polychaeta / physiology*
Population Density*
Reproduction / genetics
Sex Differentiation / physiology*
Spermatozoa / physiology

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