Oocyte growth, gonadosomatic index, hepatosomatic index and levels of reproductive hormones in goldspot mullet Planiliza parsia (Hamilton, 1822) reared in captivity

Abstract

Goldspot mullet Planiliza parsia (Hamilton, 1822) is a commercial food fish in South-east Asian countries. Availability of hatchery produced seed is the major bottleneck in the development of aquaculture of this species. Therefore, an attempt was made to develop captive broodstock of P. parsia and understand its reproductive maturation. Broodstock reared for eighteen months were sampled and six maturation stages were defined (I-VI) in both the sexes. Ovarian biopsy, gonad histology, gonadosomatic index (GSI), hepatosomatic index (HSI) and reproductive hormones assay were performed in different maturation stages. Diameter of pre-vitellogenic, vitellogenic, post-vitellogenic and ripe oocytes was less than 369.80, 444.38, 477.41 and 665.5 µm, respectively. In the female, the highest value (p<0.05) of GSI (18.31±1.15), HSI (1.84±0.84), 17 β-estradiol (E2) (898.45±0.35 pg ml-1), follicle stimulating hormone (FSH) (81.14±40.48 ml U ml-1) and vitellogenin (Vtg) were found at stage IV, whereas luteinising hormone (LH) attained its peak at V stage. In males, the concentration of testosterone (T) increased gradually from stage I (7.60±0.43 pg ml-1) to VI (40±2.89 pg ml-1). Histological observations revealed synchronous type of oogenesis and cystic type of spermatogenesis. The results of this study will help in the captive seed production of this species.

Keywords: Captive maturation, Histology, Ovarian stages, Reproductive hormones, Vitellogenin