| 摘要: |
| 砗磲是世界上最大的双壳贝类，与虫黄藻共生，生长过程中受到多种自然环境因素的影响。近年来，由于人类的过度捕捞，砗磲数量骤减，对砗磲进行人工培养、繁育、放流，成为砗磲保护的重要工作之一。此外，砗磲碳酸盐壳体还是一种良好的高分辨率古气候研究载体，但其壳体地球化学指标的环境指示意义还存在较大争议，实验室培养也是探讨砗磲地球化学指标环境指示意义的有效途径之一。基于上述原因，近年来有不少研究开展了砗磲的培养试验，通过改变培养条件分析各种环境因子对砗磲生长及壳体地球化学特征的影响。本文就砗磲的培养方法、人工培养条件进行简要综述，并从温度、光照、盐度、pCO2、营养盐、金属离子等多个方面对人工培养条件下，砗磲生长的影响因素及其生理适应性机制进行总结分析，为后续砗磲的培养保护和地球化学研究提供参考。 |
| 关键词: 砗磲 虫黄藻 砗磲实验室培养 |
| DOI：10.7515/JEE221027 |
| CSTR： |
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| 基金项目:国家杰出青年科学基金（42025304）；中国科学院战略性先导科技专项（XDB40010200） |
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| Research progress of factors influencing the growth of Tridacna and its artificial cultures |
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YANG Haotian, LIU Chengcheng, ZHAO Nanyu, LI Jun, LI Xuxiang, YAN Hong
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1. School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China
2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
3. Xi’an Institute for Innovative Earth Environment Research, Xi’an 710061, China
4. South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
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| Abstract: |
| Background, aim, and scope Giant clams (Tridacna spp.) are the largest marine bivalves of any ocean. They stay in one location and live in symbiotic relationship with zooxanthellae. Many environmental factors can affect their growth over their life time. In recent years, the number of Tridacna individuals have decreased dramatically, and some species have come close to extinction due to overfishing by humans. Artificial breeding and release of giant clams have become important elements in giant clams’ conservation. In addition, the carbonate shells of giant clams can provide valuable high-resolution paleoclimate research archives, however, the full environmental implications of shell geochemical proxy values are still to be fully understood. Laboratory controlled culture methods to reveal the environmental implication of geochemical proxy formation is an essential part of increasing our understanding. In recent years, some culture experiments have been conducted to investigate the effect of environmental factors on growth of the giant clams. Here, the influencing factors on Tridacna growth are reviewed, providing reference points for further culture, conservation, and geochemistry of giant clam shell carbonate properties. Materials and methods Here, the culture modes of Tridacna are illustrated and the environmental factors, such as temperature, light, salinity, pCO2, selected metal ions are reviewed. Results Studies have shown that the Tridacna culture modes can be divided into primary environment culture: semi-natural culture, and laboratory culture. The Tridacna survival rate under the first two culture modes and the influence of various environmental factors on the third mode are analyzed. Prolonged temperatures above 30℃ can cause damage to the Tridacna and its symbiotes. When the luminous flux exceeds 1061 μmol·m−2·s−1, the Tridacna shell will dissolve more than calcium. Tridacna gigas could adapt to lower water salinity by adjusting its respiration rate and zooxanthellae density and volume. Discussion Primary environment culture may be the most suitable mode to quantify Tridacna growth, but the survival rate is hardly guaranteed due to the presence of predators and unsuitable climatic conditions. Laboratory culture can solve this problem. However, it must be noted that the environmental factors still influence the growth of Tridacna. Studies have found that the Tridacna have the ability to adapt the changes of environment in the short term, and maintain physiological balance by changing respiratory rate, reducing metabolism, and adjusting zooxanthellae density. Some studies have also explored Tridacna genetics. It was found that Tridacna may control the up-regulation or down-regulation of differentially expressed genes, and adjust amino acid composition to adapt to the environment. Conclusions Although Tridacna can adapt to the changes of surrounding environment; if changes of environmental factors exceed certain thresholds, the adaptive capacity of Tridacna decreases. Eventually, when the growth of Tridacna is interrupted, the shell dissolves, the mantle is bleached and can be life-threatening. Different species or sizes of Tridacna have different tolerance ranges, and may have different responses to the same environmental conditions. Recommendations and perspectives In laboratory seawater tanks, it is necessary to introduce normally co-habiting animals to help the growth of Tridacna, including mint shrimp to remove algae, sea cucumbers to help turn sand, and trochids to resist Oncomelania. Thus, in addition, it is important for researchers to recognize that in nature other organisms are essential for healthy Tridacna populations. |
| Key words: Tridacna zooxanthellae Tridacna laboratory culture |
