A comparative analysis of the growth, survival and reproduction of Crassostrea hongkongensis, Crassostrea ariakensis, and their diploid and triploid hybrids

Abstract

Although the market demand for Crassostrea ariakensis is lower than Crassostrea hongkongensis in southern China, it has some advantages over C. hongkongensis, such as higher salinity tolerance and better stress resistance. Here, we present the first report of a systematic comparative study on the two native sympatric oysters of southern China, C. hongkongensis and C. ariakensis, and their diploid and triploid hybrids. Three replicates were successfully conducted, and each replicate contained two intraspecific crosses (AA–C. ariakensis♂ × C. ariakensis♀ and HH–C. hongkongensis♂ × C. hongkongensis♀), a diploid interspecific hybridization (HA–C. hongkongensis♀ × C. ariakensis♂) and a triploid interspecific hybridization (HHA). Fertilization rates of intraspecific crosses were significantly higher than those of interspecific crosses, but HA grew significantly faster than the two intraspecific crosses during the larval stage. The D larval rates of all diploids were significantly higher than that of HHA, and HHA larvae had significantly lower survival rates than diploids. At the high salinity site (Zhulin), the shell heights of HA were significantly higher than those of HH (90–600 days) and AA (270–600 days). The whole weights of HA were always significantly higher than those of the intraspecific crosses. At the low salinity site (Dafeng River), HA always had significantly higher shell heights than AA and had similar shell heights to HH. HA had higher whole weights than AA on the 360th and 480th days. In summary, data analysis revealed that HA always exhibited positive heterosis at both sites, indicating that it had growth advantages regardless of different environmental conditions. At both sites, the growth traits of HHA were significantly higher than those of HA. Our trials also demonstrated that HA had a greater salinity tolerance than the two pure species. HA was completely fertile, but 40%–48% of the HHA exhibited either significant sterility with atrophic gonads and no mature gametes or residual sterility with partly atrophic gonads and some mature gametes. Our study confirms the clear advantages of HA and HHA in terms of growth traits and viability, and provides promising evidence of their potential value as new variants for use in farming.