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Seasonal and diurnal rhythms of thyroidal status in the rainbow trout, Salmo gairdneri Richardson
Author(s) -
Osborn R. H.,
Simpson T. H.,
Youngson A. F.
Publication year - 1978
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1978.tb04199.x
Subject(s) - rainbow trout , salmo , biology , triiodothyronine , radioimmunoassay , medicine , hormone , endocrinology , circadian rhythm , zoology , diurnal temperature variation , trout , seasonality , fish <actinopterygii> , fishery , ecology , atmospheric sciences , geology
The concentrations of thyroxine (T 4 ) and triiodothyronine (T 3 ) in the blood plasma of rainbow trout ( Salmo gairdneri Richardson) at intervals throughout the year have been measured by a chemically specific gas‐liquid chromatographic (GLC) method. Mean hormone levels showed a seasonal variation, maximal levels of both hormones occurring in winter and minimal concentrations in mid summer. An apparent secondary maximum in mean T 4 and T 3 concentrations was observed in spring. (T 4 )/(T 3 ) ratios have been found to be highest in winter and lowest in summer. A radioimmunoassay procedure, validated by GLC analyses, revealed the presence of a diurnal rhythm in serum T 4 levels of trout sampled in September and in April.