Growth and reproduction of eyestalk ablated penaeus canaliculatus (Olivier, 1811) (crustacea:Penaeidae)

Abstract

The effects of single (unilateral) eyestalk ablation on the growth and reproduction of male and female Penaeus canaliculatus (Olivier) were compared with those of unablated (control) individuals. Prawns ≤ 10 mm in carapace length ablated in the premoult stage suffered high mortality. Prawns recognized as immature when ablated always moulted irrespective of their moulting stage; ovaries in females did not become vitellogenic nor did spermatogenesis occur in males. Mature females ablated in the premoult stage underwent moulting while those in the postmoult stage developed mature ovaries. Mature males in the postmoult or intermoult stages took longer to moult than those that were in the premoult stage when ablated. The Von Bertalannfy equations describing growth in P. canaliculatus were as follows: L t = 25.6 [1−e −0.0756(t−t o) ]for ablated males; L t = 25.3 [1− e −0.059( t− t o ) ] for unablated males; L t = 37.2 [1−e −0.048(t−t o) ] forablated females; L t = 33.4 [1− e −0.044( t− t o )] for unablated females. Differences in the growth rates were a result of both the moulting frequency and the increment in size at moult. However, the relative contribution of these two factors to growth varied with sex as well as with size. In both sexes, ablated individuals became sexually mature earlier; females spawned earlier. Although moulting frequency and the total number of spawns were greater for ablated females, the mean number of eggs produced (per spawn as well as total) by unablated females was higher and the mean hatching success was better.