Progressive researches for improving new methods in the field of prawn cultivation and investigations for understanding environmental factors affecting on growth and developmental periods of these animals are continuously under develop.
Giant freshwater prawn (Macrobrachium rosenbergii), from economic point of view and also from research point of view is one of the most important species of crustaceans. The effect of photoperiods on the endocrine and survival stages of this prawn has attracted many investigators. The purpose of this research was to understand the effect of three different photoperiod regimens (dark, dark-light and only light) during larval growth on metamorphosis and survival rate of Macrobrachium rosenbergii larva. Sampling and recording of larval characteristics at different periods of metamorphosis showed that the larval stages significantly were faster in the group exposed only in light regimen, so that, the mean time of metamorphosis of this group was 4 days less than other 2 groups. In addition to this fact, the survival rate of larva in light regimen significantly was higher than other groups.