International Journal of Marine Science, 2025, Vol.15, No.5, 233-244 http://www.aquapublisher.com/index.php/ijms 240 structural variation analysis can also be used to evaluate the adaptability of populations to salinity changes. For example, by comparing the genomes of historical and current populations, it is possible to determine whether they already have a recessive variation basis for adapting to higher salinity. This is of reference value for predicting the impact of increased salinity along the coast on oyster populations under global climate change. Figure 3 Genome feature survey and trio sequencing reads partition based on k-mer analysis (Adopted from Qiu et al., 2024) Image caption: (A–C) GenomeScope analysis for male C. angulata (A), female C. gigas (B), and the hybrid offspring (C), respectively. x-axis: the sequencing reads coverage. y-axis: the 21-mer frequency. (D) The distributions of 25-, 50-, 75-, and 100-mers in the AN (C. angulata) and GI (C. gigas) short sequencing reads. x-axis: k-mer length. y-axis: k-mer count. (E) The offspring reads partition by unique k-mers. x-axis: reads partition types. y-axis: the percentage of the reads. AN: reads that only contain C. angulata unique k-mers. GI: reads that only contain C. gigas unique k-mers. NN: reads that do not contain C. angulata or C. gigas unique kmers. AG: reads that containC. angulataandC. gigas unique k-mers (Adopted from Qiu et al., 2024) 7 Case Analysis: Adaptation Mechanism of Oysters to High Temperature Stress 7.1 Effect of high temperature stress on oyster survival rate and metabolic pathway High summer temperatures often trigger large-scale deaths of oysters and are considered one of the greatest environmental stresses on the oyster industry and populations in the context of global warming. When the ambient temperature exceeds the oyster tolerance range (usually >30 °C), the steady state in the oyster body will be severely disrupted. High temperatures can destroy the immune balance of oysters. Studies have shown that under continuous stress at 30 °C, the total hemolymphological antioxidant capacity (T-AOC) of Pacific oysters and Kumamoto oysters and their hybrid offspring decreased significantly, and the activity of several key immunoselectrons was also significantly reduced (Jiang et al., 2022). This means that high temperatures lead to increased oxidative stress in oysters and impaired immune system functions, which is one of the causes of oysters susceptible pathogens or direct death. Secondly, high temperatures will affect the metabolism and energy expenditure of oysters. To combat heat stress, oysters need to synthesize large amounts of molecular chaperone proteins (such as HSPs) and antioxidants, which consume a lot of energy. At the same time, high temperatures accelerate the metabolism of organisms and increase oxygen consumption. In the intertidal zone with limited dissolved oxygen, high temperatures often occur at the same time as hypoxia, which makes oysters face a "double blow": on the one hand, more oxygen is needed to support the stress response, and on the other hand, the environmental oxygen supply is reduced, leading to an energy crisis. Studies have found that oysters mobilize
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