The evolutionary consequences for seawater performance and its hormonal control when anadromous Atlantic salmon become landlocked

• Populations of anadromous fish have become landlocked in relatively recent geological history (< 14,000 years), but the evolutionary impacts of this altered lifecycle on traits underlying seawater performance have not been established. In order to examine the effects of relaxed selection on seawater traits, anadromous and landlocked Atlantic salmon were reared under identical conditions and examined for differences in seawater performance and its underlying physiological and endocrine control during the time of spring downstream migration. Salinity tolerance, survival and initial growth in seawater were greater in anadromous than in landlocked salmon. Abundance of the seawater isoform of gill Na+/K+-ATPase increased in spring in both strains but was greater in anadromous salmon. Hormones associated with seawater acclimation (adrenocorticotropic hormone, cortisol and growth hormone) increased in spring in both strains but were higher in anadromous salmon, whereas plasma thyroid hormones did not differ. Hypothalamic urotensin I mRNA levels also increased in spring and were higher in the anadromous strain. The results provide evidence that salinity tolerance and associated physiological traits are regulated by seasonal stimulation of the hypothalamic-pituitaryinterrenal axis, and that relaxed selection on seawater entry traits has decreased this stimulation in landlocked salmon.

Ämnesord

NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

Nyckelord

caudal neurosecretory-system

growth-hormone

urotensin-i

population-structure

gene-expression

salar l.

gill

smolt

prolactin

salinity

Science & Technology - Other Topics

cormick sd

1994

aquaculture

v121

p235

ote cj

1992

canadian journal of fisheries and aquatic sciences

v49

p99

cormick sd

1993

canadian journal of fisheries and aquatic sciences

v50

p656

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