Delay of the egg activation process in the Black Tiger Shrimp Penaeus monodon by manipulation of magnesium levels in spawning water

摘要

The aim of this study was to determine whether magnesium (Mg2+) in seawater is required for egg activation of the black tiger shrimp Penaeus monodon and whether manipulation of Mg2+ levels can be used to delay the process and thereby synchronize egg activation. Female P. monodon broodstock were allowed to spawn in artificial seawater containing Mg2+ at varying levels with respect to the normal (100%) level: 100%, 50%, 20% and 0%. Egg activation occurred normally at 100% Mg2+, incompletely at 50% and 20% Mg2+ levels and did not occur at all with 0% Mg2+. The fertilization rate with 100% Mg2+ was observed to be 83%, but fertilization failed to take place in all the other groups. The fertilization rate was restored from 0% to 76% following the 20% Mg2+ level treatment when Mg2+ levels returned to normal (100%) as soon as spawning was completed. This study suggests that the level of Mg2+ in seawater plays a vital role in P. monodon egg activation, and that commencement of this process could be delayed by manipulation of the Mg2+ level during and immediately after spawning.