Different responses between orange variant and cultured population of the Pacific oyster Crassostrea gigas at early life stage to temperature-salinity combinations

Although breeding of rare shell colour variants has drawn widespread attention from shellfish breeders, the potential disadvantages of their adaptive capacity have been ignored in practice. To explore the difference in adaptive capacity between orange shell variant (OSO) and commercially cultured population (CPO) of the Pacific oyster Crassostrea gigas at early life stage, the development to D-larvae and larval survival and growth (just 23 and 30 degrees C for larval experiment) of them were compared under different temperature (16, 23 and 30 degrees C) and salinity (17, 25 and 33 psu) combinations. In this study, at 23 degrees C and 25 psu, for both OSO and CPO there was no difference in fertilization rates and survival (p > .05) (mean percentages of D-larvae after fertilized 40 hr >= 95.00%; mean larval survival rates on day 10 > 80.00%). However, the percentage of D-larvae of CPO at 40 hr was significantly (p < .05) higher than OSO at temperatures of 16 and 30 degrees C and 25-33 psu and 17 psu at 23 degrees C. Similarly, CPO has a better larval survival on day 10 and growth than OSO at salinities of 17 and 33 psu at 23 degrees C. Overall, our results indicate that OSO can have an equally good performance like CPO at early life stage under optimal condition (23 degrees C; 25 psu), but the potential disadvantages in adaptive capacity will be shown at suboptimal conditions. These findings can guide future hatchery breeding of OSO, and suggest the potential disadvantages in adaptive capacity in rare colour variants need more attention in further breeding.