Seasonal changes of thyroid hormones in field‐collected Atlantic cod in relation to condition indices, water temperature and photoperiod

Abstract

Serum T 4 and T 3 in wild Atlantic cod Gadus morhua ranged from 1 to 12 ng ml 1 and from 2 to 27 ng ml 1 respectively over a 3-year period. In general, the concentrations increased from summer (T 3 ) or early autumn (T 4 ) to maxima in mid-winter and declined abruptly during spring. The T 4 /T 3 monthly means were lowest in summer and highest in winter. The seasonal patterns of thyroid hormones were weakly correlated with changes in water temperature. However, both T 4 and T 3 co-varied simultaneously with photoperiod. In addition, T 3 was correlated with the hepatosomatic index and condition factor during summer and autumn. It is suggested that the seasonal changes in the release of T 4 from the thyroid were photoperioddriven, and that the course of T 3 was regulated by the metabolic state of the fish during the somatic growth period. 2000 The Fisheries Society of the British Isles

Changes in the role of the thyroid axis during metamorphosis of the Japanese eel, Anguilla japonica

“…In an experimental stream, fish with a high level of plasma T4 swam upstream (migrant), while fish with a low level of T4 swam downstream or stayed in the stream where they were released (nonmigrant). Correlation between migratory behavior and plasma thyroid hormone levels were also observed in the Atlantic charr, Salvelinus alpines (Hogasen and Prunet,'97), and the cod, Gadus morhua (Comeau et al, 2000(Comeau et al, , 2001.…”

Discovery of latitudinal gradient of triidothyronine concentrations in ectotherms as revealed from a cyprinid fish, the common roach Rutilus rutilus

“…Further studies of latitudinal TH variation performed at different seasons are needed for a clearer understanding of this phenomenon. Remarkably, some cold-water teleosts such as the Atlantic cod Gadus morhua L. possess a reversed seasonal profile exhibiting a maximal TH level during the coldest period of year (Comeau et al, 2000). Perhaps comparable mechanisms are involved in both latitudinal increases of serum T 3 levels in common roach along a southenorth axis and increase of TH levels during seasonal lowering of temperature in Atlantic cod.…”

“…The serum levels of THs are known to fluctuate seasonally in fish (see reviews in: Leatherland, 1982;Eales and Brown, 1993;Comeau et al, 2000). These variations are associated with seasonal climate changes, thermal regime of water bodies, photoperiodism, breeding cycle (Cyr and Eales, 1996;Pavlidis et al, 2000;Eales, 2006), and migration (Baggerman, 1962;Comeau et al, 2001;Kitano et al, 2012).…”

Dopaminergic systems in the European eel: characterization, brain distribution, and potential role in migration and reproduction

“…Thyroid hormones are proposed to play a role in migratory behavior in salmonids (for review : Iwata, 1995, Specker et al, 2000 and cod (Comeau et al, 2000), and also in birds (Pathak & Chandola, 1984;Pant & Chandola-Saklani, 1993). Moreover, enhanced locomotor activity has been correlated with elevated thyroid hormone levels in American eels, A. rostrata (Castonguay et al, 1990), and most recently in A. anguilla glass eels (Edeline et al, 2005).…”