Effects of salinity and temperature on growth and survival of diploid and tetraploid larvae of the Pacific oyster, Crassostrea gigas

Abstract

Tetraploid of Crassostrea gigas was first reported in the 1990s, but its biological characteristics are seldomly known. To understand the adaptation of tetraploid larvae to salinity and temperature, the effects of salinity treatments (10, 15, 20, 25 and 30 psu) and temperature treatments (18, 23 and 28 °C) on the growth and survival of tetraploid and diploid larvae were comparatively studied. In salinity treatments, the accumulative survival rate (ASR) and relative growth rate (RGR) of tetraploid larvae were generally lower than that of diploid larvae (P < 0.05). The maximum ASR and RGR of tetraploid larvae occurred at 30 psu, with the values of 41.09% and 152.91%, respectively. At day 16, the maximum difference in ASR between diploid and tetraploid larvae was 36.41% at 20 psu, and the maximum difference in RGR of diploid and tetraploid larvae was 62.36% at 10 psu. The ASR and RGR of tetraploid larvae were lower than that of diploid larvae under temperature treatments (P < 0.05). The maximum ASR and RGR of tetraploid larvae occurred at 28 °C, with the values of 19.67% and 235.40%, respectively. The ASR of both diploid and tetraploid larvae decreased sharply in the first four days. The RGR of larvae at 18 °C was much lower than that at 23 °C and 28 °C (P < 0.05). Hence, a salinity range of 25–30 psu and a temperature range of 23–28 °C are suitable culture conditions for tetraploid larvae. These results indicate that the natural environment conditions can meet the temperature and salinity requirements for the survival and growth of tetraploid larvae. However, tetraploid larvae are less adaptable to temperature and salinity than diploid larvae. The environmental adaptability of tetraploid needs further improvement.