Effect of Rearing Container’s Colour on Metamorphosis and Survival of Larvae of Macrobrachium rosenbergii (De Man, 1879).

Macrobrachium rosenbergii larvae (IV stage) were reared in tubs having different colours viz, white, red, blue, dark-violet, grey and green. The time required for the appearance of first post-larvae was observed to be 37.3, 32.0, 29.5, 27.5, 34.0 and 35.8 days and the total amount of time required for obtaining post-larvae was 41.8, 36.3, 33.0, 31.5, 39.0 and 40.0 days in white (T1), red (T2), blue (T3), dark-violet (T4), grey (T5) and green (T6) colours respectively. Significantly less time was required for the metamorphosis of larvae to post-larvae in dark-violet tub as compared to other colours. However, there was no significant difference in grey and green colour treatments. Significantly higher survival (61.38%) was observed in dark-violet colored treatment, followed by 57.88% in blue, 51.63% in red, 43.38% in grey, 35.75% in green and 27.25% in white coloured tubs. The water parameters such as salinity, temperature, pH and dissolved oxygen were observed during the experimental period and were found to be within tolerance limit of M. rosenbergii zoeal larvae. Light-intensity in water varied in the range of 33.00 to 94.75 lux, 25.75 to 80.50 lux and 20.00 to 68.00 lux at 11:00, 15:00 and 18:00 hrs respectively in dark-violet, blue, red, grey, green and white colours. A significant difference (P 0.05) in light-intensity was observed in various treatments. Significantly maximum light-intensity was recorded in white tub and minimum in dark-violet tub. Darker internal colour of rearing tubs significantly reduces the metamorphosis period and increases survival rate of larvae of M. rosenbergii.