The effect of different pH and photoperiod regimens on the survival rate and developmental period of the larvae of Portunus pelagicus (Decapoda, Brachyura, Portunidae).

摘要

This study was conducted to determine the effects and optimum range of pH and photoperiod on the survival rate and developmental period of Portunus pelagicus larvae. The collected crab eggs were hatched and the larvae were divided into the following treatment conditions: larvae were exposed to different pH values of 7.5+or-0.1 (treatment 1), 8.1+or-0.1 (treatment 2), and 8.5+or-0.1 (treatment 3), while the temperature; salinity; and photoperiod were 28.00+or-0.1 degrees C; 35 ppm; and 12hL:12hD, respectively. The other groups of larvae were subjected to different photoperiod regimens of 6hL:18hD (treatment 1), 12hL:12hD (treatment 2) and 18hL:6hD (treatment 3), while the temperature, salinity and pH were maintained at 28.00+or-0.1 degrees C, 35 ppm and 8.1+or-0.1, respectively. Results revealed that the average overall survival rates and developmental period during the different pH treatment were not significantly different. It was also observed that the differences in the average overall survival rates and developmental period among the photoperiod treatments were not significant. The average larval developmental period for the parameters tested was 16 days. It is suggested that the most suitable pH is 8.0+or-0.1 and the favourable photoperiod regimen is 12hL:12hD as these conditions achieved the highest survival rate and lowest developmental period for the crabs.