Effect of eyestalk ablation on ovarian maturation and spawning in green tiger shrimp Penaeus semisulcatus (De Haan 1844)

Effect of unilateral eyestalk ablation on ovarian maturation and spawning in Penaeus semisulcatus was studied in indoor cement tanks. Induction of maturation in ablated female shrimps was studied at two different light intensities with the experimental animals forming the following four groups: ablated shrimps maintained in tanks provided with shading (light intensity at 10 Lux) (T1), unablated females maintained in tanks with shading (T2), ablated shrimps in tanks with out shading (receiving light intensity at 400 Lux). (T3), and unablated females in tanks without shading (T4). Earliest spawning occurred on the 7, 14, 14, and 11th day in the treatment groups T1, T2, T3, and T4 respectively. Ovarian maturation in ablated shrimps maintained in tanks receiving dim light was significantly (p<0.05) faster than that in the other treatments, and females in T1 spawned repeatedly. The number of spawnings per female was also significantly affected by treatments (p<0.05), the average number of spawnings per female was 1.88±0.08 for ablated animals receiving dim light (T1), 0.08± 0.01 for non–ablated animals exposed to dim lighting (T2), 0.21±0.02 for ablated shrimps receiving bright light (T3), and 0.02±0.00 for non-ablated animals receiving bright light (T4). Eyestalk ablation was found to have no significant effect on egg quantity/spawning, egg hatching rate and nauplii quantity (p＞0.05), while eyestalk ablated animals had significantly higher mortality rate (p< 0.05).