ROLE OF NEUROENDOCRINE MODULATORS ON GONADAL MATURATION IN RAINBOW SHARK, (Epalzeorhynchos frenatum)
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Date
2015
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Fisheries College and Research Institute, Thoothukudi, Tamil Nadu Dr.J.Jayalalithaa Fisheries University
Abstract
The present investigation was undertaken to ascertain the effect of neuroendocrine modulators on gonadal maturation in Rainbow shark, Epalzeorhynchos frenatum. The gonadal maturation was observed using three different hormones viz., GnRH, hCG and synthetic Kisspeptin-10. The fishes were divided into four groups .First, second and third groups of fishes were injected intramuscularly with GnRH, hCG and synthetic Kisspeptin-10 respectively. The fourth group was maintained without any hormone injection as control. A duplicate set was also maintained simultaneously. Each hormone was injected at three different concentrations. Male and female fishes were stocked in separate tanks. Monthly sampling of gonads and blood samples were also collected from control and hormone (GnRH, hCG and synthetic Kisspeptin-10) injected fishes during the experimental period to assess the maturation using various reproductive parameters, such as Gonadosomatic index (GSI), fecundity and ova diameter. GSI values of synthetic Kisspeptin-10 injected fishes were higher than other two hormones and control fishes in most of the sampling period. The synthetic Kisspeptin-10 injected male and female fish attained highest GSI values (1.49 & 8.7) at the end of the experimental period. Maximum fecundity of 5040 eggs was observed at the end of the sampling period in the synthetic Kisspeptin-10 hormone treated fishes. The maximum ova diameter of 0.84 mm was observed from synthetic Kisspeptin-10 injected fishes, whereas in control fish it was 0.56 mm. Changes in the testosterone and estradiol-17 level was observed from the hormone injected fishes when compared to the control fish. Maximum testosterone and estradiol-17 level of 8.34 ng/ml and 439 pg/ml of blood was observed from synthetic Kisspeptin- 10 injected male and female fishes respectively. Histological changes in the ovary and testis of synthetic Kisspeptin-10 injected male and female fish showed the presence of advanced maturity stages of gonads during all sampling periods. Four types of growing oocytes namely perinucleolar, previtellogenic, vitellogenic and hydrated oocytes were observed in the ovary of E. frenatum. Similarly in testis, five types of spermatogenic cell types were identified namely spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa. Induced breeding experiments were carried out with GnRH, hCG and synthetic Kisspeptin-10 at the rate of 0.5 mg/kg, 1500 IU/kg and 150 μg/kg respectively. Among the three treatments, fishes induced with 150 μg/kg body weight of synthetic Kisspeptin-10 performed better result than the other two groups of the hormone induced fishes.
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