Effect of eyestalk extirpation on haemolymph ionic concentration of Metapenaeus monoceros

Abstract

Metapenaeus monoceros in the size range 65-70mm was subjected to the evaluation of sodium(Na⁺),, potassium (K⁺) and calcium (Ca²⁺) ionic concentration in the haemolymph after unilateral (UEA) and bilateral eyestalk ablation (BEA) in 6 (low), 16(medium) and 35(high)PSU salinity levels. The present investigation suggests the possible presence of a Na⁺ regulating factor in the eyestalks of M. monoceros as the regulation of these ions was observed to be affected in destalked prawns (P<0.05). The K⁺ concentration showed differences among the ablated and control prawns (P<0.05). The BEA prawns registered an increased concentration of K⁺ by 11.7%, 13.1% and 16.0% at the three salinities compared to controls. Among the UEA prawns the differences in the average concentration of K⁺ compared to control were 1.5, 0.33 and 11.3% at low, medium and high salinity levels. The concentration of Ca²⁺ in the BEA prawns registered a decrease by 21% at low, 19% at medium and 22% at high salinity whereas in the UEA prawns, an increase by 5.5%, 0.7% and 5.2% at these three salinity levels was observed compared to control prawns. Thus it can be inferred that, UEA prawns at 35PSU could be recommended for better growth of M. monoceros in culture conditions.