Reproductive performance and vitellogenin gene expression on female Bonylip barb (Osteochilus vittatus) during its reproductive cycle under culture conditions

Abstract

The Bonylip barb is a tropical fish indigenous to Southeast Asia and has high cultivation potential. The reproductive performance and vitellogenin gene expression were studied during the female brooders’ reproductive cycle for 16 wk. Ovulation was induced in 30 fish using Ovaprim (0.5 mL/kg bodyweight) followed by artificial spawning. Every 2 wk, three subsamples were sacrificed. Ovary and liver samples were collected to observe the reproductive performance based on the gonadosomatic index (GSI), hepatosomatic index (HSI), ovarian histology and spawning performance at weeks 8, 12 and 16, and vitellogenin gene expression using real-time quantitative polymerase chain reaction. The GSI increased significantly (p < 0.05) towards week 16 (mean ± SD; 19.15 ± 3.88), whereas the HSI showed a constant pattern. Ovary histology showed asynchronous development of oocytes. The oocyte composition indicated the developing phase from week 0 until week 4 and the spawning-capable phase from week 6 onward. The relative Vtg1 and Vtg2 gene expression levels in the liver increased significantly in the developing (week 4: Vtg1 16.72 ± 7.08; Vtg2 20.02 ± 1.19) and beginning of spawning-capable phases (week 6: Vtg1 37.97±7.76; Vtg2 22.86±2.69) and declined from week 8 onward. The spawning performance, particularly mature egg diameter, fertilization rate, hatching rate, larval survival at 3 d post hatching (dph) and abnormalities until 10 dph were significantly higher at weeks 12 and 16 than at week 8. Despite the fecundity, the survival rate at 10 dph and abnormalities until 3 dph did not differ significantly at each observation time. Therefore, a relationship between the GSI, ovarian histology and Vtgs gene expression influenced the spawning performance of the female Bonylip barb.