Increased daylength stimulates plasma growth hormone and gill Na+, K+-ATPase in Atlantic salmon (Salmo salar)

S. D. McCormick, B. Th Björnsson, M. Sheridan, C. Eilerlson, J. B. Carey, M. O'Dea

Research output: Contribution to journalArticle

113 Scopus citations

Abstract

Atlantic salmon juveniles reared at constant temperature (9-10°C) were exposed to four photoperiod treatment and sampled every 2 weeks from January through May. Fish reared under normal photoperiod exhibited eight-and three fold increases in plasma growth hormone and gill Na+, K+-ATPase activity, respectively, between January and April. Fish exposed to abrupt increases in daylength (LD 15:9) in February or March responded with earlier increases in plasma growth hormone and gill Na+, K+-ATPase activity, and earlier decreases in condition factor relative to fish in the normal photoperiod group. Fish maintained under short daylength (LD 9:15) from January to May exhibited delayed and muted increases in plasma growth hormone and gill Na+, K+-ATPase activity. Plasma thyroxine exhibited a 2.5-fold increase from February to late March in the normal photoperiod group, was generally lower in the LD 9:15 group, but exhibited no obvious response to abrupt increases in daylength. There was an increase in plasma 3,5,3′-triiodo-l-thyronine with time in all groups (43-80%) but no significant response to photoperiod. Plasma levels of somatostatin-25 were highest in the LD 9:15 group, but there was no detectable response to increased daylength in any of the photoperiod treatments. The results indicate that plasma growth hormone is responsive to increased daylength and may be causally related to subsequent increases in gill Na+, K+-ATPase.

Original languageEnglish
Pages (from-to)245-254
Number of pages10
JournalJournal of Comparative Physiology B
Volume165
Issue number4
DOIs
StatePublished - Sep 1995

Keywords

  • Ion transport
  • Photoperiod
  • Smolt
  • Somatolactin
  • Thyroid hormones

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