Growth, survival and gonad development of diploids, triploids and tetraploids of ?Haida No. 3? line of the Pacific oyster Crassostrea gigas

Selection and polyploidization are two practical tools for improving productive traits of oysters. To evaluate the aquaculture traits of diploids, triploids and tetraploids of 'Haida No. 3' line of the Pacific oyster Crassostrea gigas, four mating combinations (HD-diploid 'Haida No. 3' line female x diploid 'Haida No. 3' line male, HTR-diploid 'Haida No. 3' line female x tetraploid 'Haida No. 3' line male, HTE-tetraploid 'Haida No. 3' line female x tetraploid of 'Haida No. 3' line male, WD-wild diploid female x wild diploid male) were established. At both Rongcheng and Rushan sites, HD had a larger shell height and wet weight than WD. HTR outperformed HD in growth and survival, with a consistently positive value of triploid advantage (TA). On the day 480 at Rushan site, the triploid advantages in terms of shell height, wet weight and cumulative survival were 20.70%, 40.28% and 29.27%, respectively. HTE were the lowest in growth and survival compared to the other three groups. Histomorphometric analysis revealed that HTR were partial highly sterile, indicating its gonadal atrophy and gamete abnormalities. In contrast, HD and HTE were fully fertile and contained functional gametes. During the whole culture period, HTR remained 100% triploid rate while HTE maintained a tetraploid rate of over 80%. HTR and HTE exhibited rapid growth and stable black shell color, suggesting that these traits were stably inherited by the ploidy change. Overall, our results demonstrated that polyploidization based on selective line had favorable performance for aquaculture, which would have vital practical interest for oyster culture in northern China.