Effects of Temperature on the Embryonic Development and Larval Activity of Epinephelus moara

Abstract:

In this study we investigated the effect of incubation temperatures (16℃, 18℃, 20℃, 22℃, 24℃, 28℃, and 30℃) on the embryonic development and larval activity of the Epinephelus moara. The stage of embryonic development after 12 hours of hatching, the hatching rate and the deformity rate of newly-hatched larvae were also measured and analyzed. We performed the starvation test on the newly-hatched larvae and evaluated their daily survival rate and the survival activity index (SAI) at different temperatures. It showed that the embryos could be hatched at 18−28℃. The hatching time was negatively correlated to the temperature as shown in the equation y=12139x−1.869 (R2=0.993, P<0.01), in which y was the hatching time and x was the temperature. The highest hatching rate (71.01%) and the lowest deformity rate (9.7%) were observed at 22℃. A lower hatching rate (65.37%) and higher deformity rate (13.07%) appeared at 20℃. The hatching rate decreased gradually when the temperature was below 22℃, and reached 24.39% at 18℃. The hatching rate also decreased significantly when the temperature was above 22℃, and the lowest hatching rate (16.11%) appeared at 28℃. The effect of temperature on the deformity rate of newly-hatched larvae showed an opposite pattern. The embryonic development stopped at the stage of blastula at 16℃. At 30℃, the cell dividing ceased at the embryo body stage. The SAI first increased and then decreased along with the rise in the temperature. At 20℃, SAI of the larva was the highest (25.97) with the longest half-death time of 7 d. Therefore, the optimal hatching temperature for the fertilized eggs of E. moara could be 22–24℃, and the most suitable temperature for the survival of newly-hatched larvae could be 20–22℃.