Comparative analysis of growth and metabolism in diploid and triploid Pacific oysters Crassostrea gigas under different temperature and salinity

Abstract

Triploid Pacific oyster Crassostrea gigas is increasingly important in aquaculture due to its improved growth and meat quality. However, adaptability differences between diploid and triploid oysters in varying environments are inconclusive. To address this concern, we compared the growth, physiological parameters (clearance rate, CR; oxygen consumption rate, OCR; ammonia excretion rate, AER; the Arrhenius break temperature (ABT) based on heart rate), and metabolism-related gene expression (HK, PK, and PEPCK) in diploid and triploid C. gigas at various temperatures (17 ℃, 20 ℃, 23 ℃, 26 ℃, and 29 ℃) and salinities (18 psu, 22 psu, 26 psu, 30 psu, and 34 psu). Triploids exhibited higher shell heights than diploids across various temperature and salinity treatments. No significant difference in CR, OCR, or AER was observed between diploids and triploids. Compared to diploids, triploids had higher O: N ratios at 29 ℃ but lower O: N ratios at 18 and 22 psu. Except for the 23–26 ℃ range, diploids had lower Q₁₀ values, suggesting that they are less sensitive to respiration changes within these temperature ranges. Additionally, triploids demonstrated higher thermal adaptation, as evidenced by a higher ABT value (triploids: 26.52 ℃ > diploids: 25.71 ℃). The PEPCK/PK and PEPCK/HK ratios indicated that triploids have lower anaerobic metabolism levels than diploids at 17 ℃, 23 ℃, and 26 ℃, but higher levels at salinities of 18 psu, 22 psu, and 26 psu. Overall, triploids showed greater adaptability at 17 ℃, 23 ℃, 26 ℃ and 29 ℃, while lower adaptability at salinities of 18 psu, 22 psu, and 26 psu. Our findings provide insights into the physiological metabolism underlying temperature and salinity adaptation in diploid and triploid oysters.