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Divergence in thyroid hormone concentrations between juveniles of marine and stream ecotypes of the threespine stickleback (Gasterosteus aculeatus)
Evolutionary Ecology Research (2013)
  • Jun Kitano
  • Sean C Lema

Background: Hormones regulate the expression of multiple phenotypic traits. Therefore,

divergence in hormone concentrations may lead to evolutionary changes in the coordinated

physiological and behavioural traits that comprise an organism’s integrated phenotype. Adults

of marine ecotypes of threespine stickleback (Gasterosteus aculeatus) have higher concentrations

of the thyroid hormone thyroxine (T4) than adults of stream-resident ecotypes (Kitano

et al., 2010). Thyroid hormones are well-established mediators of osmoregulation and migratory

behaviours in fish, and the difference in T4 concentrations indicates that changes in thyroid

hormone signalling may underlie the evolutionary and ecological divergence of migratory and

non-migratory ecotypes.

Questions: Is the variation in T4 concentrations present in earlier life stages where it

could contribute developmentally to differences in phenotype? Do T4 concentrations change in

marine ecotypes before seaward migration?

Organisms: A parapatric pair of marine and stream ecotypes of threespine stickleback

collected from British Columbia, Canada, and a marine ecotype collected from Washington

State, USA.

Methods: We collected juvenile fish of both marine and stream ecotypes on the same day in a

single river to compare the whole body concentrations of T4 using radioimmunoassay. We also

sampled juvenile fish of the marine ecotype in another river at three different times to determine

whether these fish exhibit temporal changes in T4 concentrations before seaward migration.

Results: Juvenile stickleback of the marine ecotype had higher T4 concentrations than

the parapatric stream-resident juveniles. The T4 concentrations in another marine population

varied slightly across sampling times before seaward migration.

Conclusions: T4 concentrations differ consistently between marine and stream ecotypes

in both juvenile and adult life stages consonant with the hypothesis of evolutionary changes in

thyroid signalling.

Publication Date
Citation Information
Jun Kitano and Sean C Lema. "Divergence in thyroid hormone concentrations between juveniles of marine and stream ecotypes of the threespine stickleback (Gasterosteus aculeatus)" Evolutionary Ecology Research Vol. 15 (2013)
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