Document Detail

A tadpole-induced polyphenism in the salamander Hynobius retardatus.
MedLine Citation:
PMID:  12449490     Owner:  NLM     Status:  MEDLINE    
Larvae of the salamander Hynobius retardatus have two distinct morphs: normal and broad-headed, cannibal morphs. We performed three experiments to differentiate among the following hypotheses: The broad-headed morph is induced to allow: (1) feeding on nutritious conspecifics; (2) exclusion of strong competitors for food or space; or (3) feeding on large, tough prey when smaller prey items are unavailable. When newly hatched larvae were reared with a heterospecific, Rana pirica (an anuran amphibian) tadpoles, the broad-headed morph was induced more frequently compared with those reared with conspecifics. The phenotype expressed depended on the size of the tadpoles: The broad-headed morph occurred more frequently with small and the normal morph with large tadpoles. Metamorphosis occurred sooner in larvae fed conspecifics compared with those fed heterospecific tadpoles, and the mean growth rate of larvae fed conspecifics was significantly faster than that of those fed tadpoles, suggesting that the heterospecific tadpoles were less nutritive than the conspecifics. These results do not support the hypotheses that the broad-headed morph evolved for consuming conspecifics because of their better balance of nutrients or for excluding strong competitors for food or space. We tentatively conclude that the morph evolved to eat large, tough prey, including both conspecifics and heterospecific tadpoles. Because H. retardatus usually spawns very early in the spring in small ponds partially covered with ice and snow, newly hatched larvae may starve from the lack of proper food owing to extremely low water temperatures. Thus, the broad-headed morph of H. retardatus may represent a cold-habitat adaptation to overcome the severe circumstance when the only food items available are relatively large conspecifics or heterospecific tadpoles.
Hirofumi Michimae; Masami Wakahara
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Evolution; international journal of organic evolution     Volume:  56     ISSN:  0014-3820     ISO Abbreviation:  Evolution     Publication Date:  2002 Oct 
Date Detail:
Created Date:  2002-11-25     Completed Date:  2003-05-28     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0373224     Medline TA:  Evolution     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2029-38     Citation Subset:  IM    
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
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MeSH Terms
Analysis of Variance
Behavior, Animal
Population Dynamics
Selection, Genetic
Species Specificity
Time Factors
Urodela / embryology,  genetics,  physiology*

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