Genetics. Published Articles Ahead of Print: June 18, 2008, Copyright © 2008
doi:10.1534/genetics.107.084251


A more recent version of this article appeared on July 1, 2008.

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The Genetic Basis of Smoltification-Related Traits in Oncorhynchus mykiss

Krista M. Nichols 1*, Alicia Felip 2, Paul Wheeler 2 and Gary H. Thorgaard 2

1 Purdue University
2 Washington State University

* To whom correspondence should be addressed. E-mail: kmnichol{at}purdue.edu.

Submitted on November 6, 2007
Revised on December 20, 2007
Accepted on 1 May 2008


Abstract

The timing and propensity for migration between fresh- and seawater is a key theme in the diversity of life histories within the salmonid fishes. Across salmonid species, life history strategies range from wholly freshwater-resident populations, to migratory and non-migratory variation within populations, to populations and species that are primarily migratory. Despite the central theme of migration to the evolution of these fishes, the genetic control of migration-related processes is poorly understood. Using a genetic cross of clonal lines derived from migratory and non-migratory life history types of Onchorhynchus mykiss (steelhead and rainbow trout, respectively), we have dissected the genetic architecture of the complex physiological and morphological transformation that occurs immediately prior to seaward migration (termed smoltification). Quantitative trait loci (QTL) analyses were used to identify the number, effects, and genomic location of loci associated with smoltification-related traits, including growth and condition factor, body coloration, morphology, and osmoregulatory enzymes during the smoltification period. Genetic analyses revealed numerous QTL, but one locus in particular is associated with multiple traits in single and joint analyses. Dissecting the genetic architecture of this highly complex trait has profound implications for understanding the genetic and evolutionary basis of life history diversity within and among migratory fishes.

Key Words: QTL, anadromy, migration, morphology, physiology