Seasonal Variations and Maturity Stages in Relation to Differences in Serum Levels of Gonadal Steroids, Vitellogenin, and Thyroid Hormones in the Common Dentex (Dentex dentex)

Seasonal Fluctuations of Sex Steroid Hormones in Indian Major Carp Catla Catla in Khouzestan, Iran

“…Similarly, a peak in 17beta-estradiol plasma concentrations associated with the synthesis of vitellogenic proteins (vitellogenin) has been described in many other teleosts [2]. This result coincided with other studies such as study on Common carp [1], Acipenser Persicus [30], Rutilus firrsi kutum [31], Labeo rohita [32].…”

“…Studies have shown that annual fluctuations of hormones related to reproductive, feeding and growth cycles in fishes [15]. Annual rhythm of hormones closely related to factors such as temperature, environment, species of fish, length of day and gonadal sex steroids [2].…”

“…Hormones are not beginner of reaction and many physiological actions undergo without them. Sex steroids have long been recognized as key hormones regulating sexual differentiation, physiological aspects of reproduction and the development of primary and secondary sexual characteristics [2].…”

Variations in the Plasma Levels of Thyroid Hormones and Testicular Activity in the Male Air-breathing Catfish (Clarias gariepinus) over the Annual Cycle

“…Seasonal variations in the levels of thyroid hormones have been reported in a number of temperate zone fish species, such as Oncorhynchus masou, Salmo gairdneri, Pseudopleuronectes americanus, Dentex dentex, and Gadus morhua (Bau and Parent, 2000;Comeau et al, 2000;Cyr et al, 1988aCyr et al, , 1998Eales and Fletcher, 1982;Leloup and De-Luze, 1985;Nishikawa et al, 1979;Pavlidis et al, 2000;Sower et al, 1992;Stryjek-Kaminska et al, 1988). Seasonal variations in the levels of thyroid hormones have also been reported in the tropical freshwater perch Anabas testudineus (Chakraborti and Bhattacharya, 1984).…”

“…Many fish species exhibit cyclical variations in plasma levels of thyroid hormones that are associated with sexual maturation (Cyr et al, 1998;Eales, 2006;Pavlidis et al, 2000), breeding cycle (Eales, 2006;Supriya et al, 2005;Volkoff et al, 1999), the regulation of oxidative metabolism (Gupta and Thapliyal, 1991;Lynshiang and Gupta, 2000;Peter and Oommen, 1987), migration (Imbert et al, 2008;Iwata, 1995;Ojima and Iwata, 2007), electrolyte and water metabolism (Klaren et al, 2005;Peter et al, 2000), and so on. These hormones help the fish continually adjust their physiological and morphological characteristics in relation to the ever-changing aquatic environment (Eales, 2006;Matty, 1985).…”