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

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 male x C. ariakensis female and HH-C. hongkongensis male x C. hongkongensis female), a diploid interspecific hybridization (HA-C. hongkongensis female x C. ariakensis male) 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.

在中国南方，虽然近江牡蛎的市场需求低于香港牡蛎，但它相对于香港牡蛎具有一些优势，例如更高的耐盐性和更好的抗逆性。在此，我们首次对中国南方这两种同域分布的本土牡蛎——香港牡蛎和近江牡蛎及其二倍体和三倍体杂交种进行了系统的比较研究。成功进行了三次重复实验，每次重复包含两个种内杂交（AA - 近江牡蛎雄性×近江牡蛎雌性和HH - 香港牡蛎雄性×香港牡蛎雌性）、一个二倍体种间杂交（HA - 香港牡蛎雌性×近江牡蛎雄性）以及一个三倍体种间杂交（HHA）。种内杂交的受精率显著高于种间杂交，但在幼虫阶段，HA的生长速度显著快于两个种内杂交组合。所有二倍体的D形幼虫率显著高于HHA，并且HHA幼虫的存活率显著低于二倍体。在高盐度位点（竹林），HA的壳高在90 - 600天显著高于HH，在270 - 600天显著高于AA。HA的总重量始终显著高于种内杂交组合。在低盐度位点（大丰河），HA的壳高始终显著高于AA，且与HH相近。在第360天和第480天，HA的总重量高于AA。总之，数据分析表明，HA在两个位点均表现出正向杂种优势，这表明无论环境条件如何它都具有生长优势。在两个位点，HHA的生长性状均显著高于HA。我们的试验还表明，HA比两个纯种具有更强的耐盐性。HA完全可育，但40% - 48%的HHA表现出明显的不育，性腺萎缩且无成熟配子，或者是残留不育，性腺部分萎缩且有一些成熟配子。我们的研究证实了HA和HHA在生长性状和生存能力方面具有明显优势，并为它们作为养殖新品种的潜在价值提供了有希望的证据。