Effects of different spawning agents on serum levels of reproductive steroid hormones and cortisol level in adult female Barbus sharpeyi (Gunther, 1874).

ABSTRACT

The question of whether, as hormone therapies, spawning agents differ from each other to induce physiological pathways of gametogenesis and oocyte maturation in fish remains important, because it could modify undesirable changes, regulated by endocrine systems of individual fish. A series of experimental treatments were applied to investigate the underlying mechanism(s) in which female bunnei (Barbus sharpeyi) fish respond differently to hormone therapies. Female broodstocks were injected twice (with 12 h interval) by three different treatments namely A, B and C. The treatment A received carp pituitary extract (CPE) + luteinizing hormone-releasing hormone analogs (LHRHα2) (0.5 mg CPE kg(-1) BW for first injection and 2 mg CPE kg(-1) BW + 10 µg LHRHα2 kg(-1) for second injection), treatment B received CPE (0.5 and 3.5 mg kg(-1) BW), and treatment C received ovaprim (0.1 and 0.15 ml kg(-1) BW). Blood samples were collected at four different time intervals, including prior to injections, 6 h after first injection, 6 h after second injection and at the time of spawning, and serum steroid hormones, including testosterone, progesterone and estradiol-17ß as well as cortisol, were measured. Results showed significant increases in serum estradiol-17ß following all treatments, but the most profound response was found in treatments A and B. Testosterone was higher in larger broodfish than in small-sized broodfish (>1.5 vs. <1.5 kg) in all treatments. CPE led to higher concentration of testosterone rather than two other treatments. CPE also increases the progesterone following first injection and approximately remains unchanged till the end of experiment. Change in progesterone level was only significant after second injection of ovaprim as well as after spawning compared with previous time. Linear regression analyses indicated that cortisol had adverse effects on progesterone and testosterone levels of weight group <1.5 kg. These results suggest that among inducing agents, applied here, CPE can provide more reasonable response in reproduction of female B. sharpeyi.