温度、盐度和密度对福建牡蛎♀×长牡蛎♂杂交子代浮游幼虫生长及存活的互作效应

Interaction Effects of Temperature, Salinity and Density on Growth and Survival of Hybrid of Crassostrea angulata♀ and C. gigas♂

摘要:

为研究温度、盐度和密度对福建牡蛎（Crassostrea angulata）♀×长牡蛎（C. gigas）♂杂交子代幼虫生长与存活的影响，采用响应面分析法，设置温度（21℃、24℃、27℃）、盐度（20、25、30）、密度（5、10、15 ind./mL）三因素三水平实验。结果显示：（1）温度与盐度的一次效应、二次效应及其互作效应对幼虫生长与存活的影响极显著（P<0.01）；（2）密度的二次效应对生长影响极显著（P<0.01），其一次与二次效应对存活的影响也极显著（P<0.01）；（3）密度的一次效应及温度与密度的互作效应对生长影响显著（P<0.05）；（4）温度与密度的互作效应对存活影响不显著，盐度与密度的互作效应对生长与存活均无显著影响；（5）三因素对幼虫生长与存活的影响程度依次为：盐度＞温度＞密度。通过响应面优化得到最适培育条件为温度25.76℃、盐度27.77、密度13.42 ind./mL，此条件下模型预测的幼虫壳高特定生长率（SGR）为7.47%/d，成活率达80.23%，模型可靠性为100%。经实验验证，验证实验在温度26℃、盐度28、密度13.5 ind./mL条件下进行，实测幼虫壳高SGR为7.33%/d，成活率为79.26%，结果与预期值相近，响应面分析方法可靠。研究表明，盐度是影响福建牡蛎与长牡蛎杂交子代浮游幼虫生长与存活的首要限制因子，温度次之，密度影响相对较小。本研究结果为牡蛎杂交子代苗种的高效培育提供了可靠的基础资料。

Abstract:

The successful development of oyster larvae during the planktonic stage is critically regulated by a complex interplay of environmental and husbandry factors, with temperature, salinity, and rearing density being paramount. These factors collectively govern physiological processes, metabolic rates, and energy allocation, ultimately determining larval growth performance, survival, and the success of subsequent metamorphosis and settlement. While the individual effects of these parameters on various bivalve species have been documented, comprehensive analyses of their synergistic or antagonistic interactions, especially for interspecific hybrid progenies with significant aquaculture potential, remain scarce. This gap limits the development of precise, efficient, and standardized protocols for mass seedling production. The hybrid offspring of Crassostrea angulata and C. gigas exhibit notable heterosis in growth and survival, presenting a promising candidate for genetic improvement in oyster aquaculture. However, optimizing their early rearing environment is essential to fully realize this potential. This study, therefore, aimed to systematically investigate the individual and interactive effects of temperature, salinity, and larval density on the growth and survival of C. angulata ♀ × C. gigas ♂ hybrid larvae and to establish an optimized rearing regime using Response Surface Methodology (RSM). A Box-Behnken Design (BBD), a highly efficient RSM model requiring fewer experimental runs, was employed. Three key factors were evaluated at three levels each: temperature (21, 24, and 27°C), salinity (20, 25, and 30), and initial larval rearing density (5, 10, and 15 ind./mL). The response variables were larval shell height-specific growth rate (SGR, %/d) and cumulative survival rate (%). D-shaped larvae were reared under the designated experimental combinations for 10 days with standardized feeding and water management. Shell height measurements and survival counts were conducted at the beginning and end of the trial. The experimental data were fitted to a second-order polynomial regression model using Design-Expert software to analyze the significance of main effects, quadratic effects, and two-way interaction effects. The results revealed a complex and differential influence of the three factors on larval performance. For larval growth (SGR): The linear, quadratic, and interactive effects of both temperature and salinity were highly significant (P < 0.01). The quadratic effect of density was also highly significant (P < 0.01), while its linear effect and its interaction with temperature were significant (P < 0.05). The interaction between salinity and density was not significant for growth. For larval survival: Temperature and salinity again exhibited highly significant linear, quadratic, and interactive effects (P < 0.01). Both the linear and quadratic effects of density were highly significant (P < 0.01). However, the interaction between temperature and density, as well as the interaction between salinity and density, did not significantly affect survival (P > 0.05). Overall, the order of influence on both growth and survival was salinity > temperature > density, underscoring the paramount importance of osmotic regulation during the early larval stage. The RSM model demonstrated excellent fit, with high coefficients of determination (R2). Model optimization, targeting the simultaneous maximization of SGR and survival, yielded the following optimal rearing conditions: temperature 25.76°C, salinity 27.77, and density 13.42 ind./mL. Under these conditions, the model predicted a shell height SGR of 7.47 %/d and a survival rate of 80.23%, with a desirability function value of 1.000. A verification experiment conducted at practically adjusted conditions (26°C, 28, 13.5 ind./mL) produced actual values of 7.33 %/d SGR and 79.26% survival. The close agreement between predicted and observed values, with relative errors below 2%, validated the high accuracy and reliability of the RSM model and the optimization results. In conclusion, this study successfully applied RSM to decode the multifactorial effects on hybrid oyster larval performance. It conclusively identifies salinity as the most critical limiting factor, followed by temperature, while density operates as a significant but secondary husbandry parameter. The significant interaction between temperature and salinity highlights the necessity for their coordinated management in hatchery practices. The derived optimal condition set provides a scientifically grounded, practical, and efficient protocol for the intensive larval rearing of this specific hybrid cross, which can directly enhance seedling production yield and consistency. Beyond immediate application, this work demonstrates the utility of RSM as a powerful tool for multivariable optimization in aquaculture research. For future investigations, it is recommended to explore the interactive effects of these factors under near-limit stress conditions to better understand the physiological thresholds and adaptive mechanisms of larvae, thereby further refining resilient breeding and rearing strategies for sustainable oyster aquaculture.