International Journal of Aquaculture, 2025, Vol.15, No.4, 197-207 http://www.aquapublisher.com/index.php/ija 198 not only help reveal the molecular basis of trait formation, but also have practical significance for formulating new varieties cultivation strategies. This study explains the physiological and molecular basis of oyster growth and stress resistance, the main epigenetic types, the regulatory effect of epigenetic on growth and stress resistance, environmental interaction, and research methods and technical prospects, and reviews the research progress in the past five years. 2 Physiological and Molecular Basis of Oyster Growth and Stress Resistance 2.1 Major physiological processes and molecular pathways related to growth The growth of oysters involves a series of physiological processes such as nutrient intake, energy distribution and tissue formation. Among them, filter feeding allows oysters to consume a large amount of plankton for growth, and digestive tissues such as the hepatopancreas play a key role in the transformation of nutrients. Endocrine axes such as growth hormone and insulin-like growth factor (GH/IGF) regulate the growth and development of shellfish, and their signals can promote protein synthesis and cell proliferation (Gawra et al., 2023). On the molecular pathway, studies have found that the expression of pathways such as ribosome biogenesis and nucleic acid metabolism in the high-growth lines of oysters is enhanced, suggesting that these pathways are closely related to rapid growth. Chitin formation (biomineralization) is also an important aspect of oyster growth, and the matrix proteins and ion transport channels secreted by the coat membrane determine the deposition rate and structure of shells (Rivière et al., 2013). Recent genomic analysis identified a batch of genes related to oyster shell formation and growth regulation. For example, several key genes controlling shell mineralization and body length were found in eastern oysters. The expression of these growth-related genes and pathways is affected by multiple factors, including nutritional level, temperature and developmental stage, and needs to be further studied in combination with an epigenetic perspective. 2.2 Key mechanisms of stress resistance: response to temperature, salinity, and pathogenic pressure Oysters’ stress resistance is reflected in their tolerance to environmental stress (such as temperature, salinity changes) and pathogenic infection. In terms of temperature stress, oysters can resist high-temperature damage through protective mechanisms such as heat shock protein (HSP). Studies have shown that sharply increasing water temperatures can induce high expression of the Oyster HSP gene, which helps protein fold and maintain cellular homeostasis. Under low temperature and dry dew (air exposure) stress, oysters tend to close both shells to reduce water dispersion and survive adverse periods by reducing metabolic rate to enter dormant state. Under salinity stress, broad-salt Pacific oysters can adapt to salinity changes by regulating the content of intracellular osmotic substances (such as free amino acids, glycerol betaine). When the ambient salinity drops sharply, oysters quickly accumulate amino acids to maintain cell osmotic balance; while under high salt conditions, free amino acids in the body are reduced to avoid cell dehydration. For pathogen invasion, oysters rely on innate immune mechanisms to resist infection (She et al., 2022). The hemolymph of oysters contains phagocytosis cells, which can actively engulf invading pathogens, such as Vibrio parahaemolyticus and Zyxozoa (shellfish parasites) that invade oysters. At the same time, oysters can produce humoral effectors such as antibacterial peptides and lysozyme to kill pathogenic microorganisms. When infection occurs, related signaling pathways such as NF-κB, TLR, etc. are activated, triggering the cascade expression of immune genes (Valdivieso et al., 2025). For example, in the study of the eastern oyster infection parasite Perkinsus marinus, high infection intensity induced a series of changes in the expression of immune response genes, accompanied by changes in the methylation level of the promoter region of some genes. 2.3 Trade-offs and interactions between growth and stress resistance There is often a trade-off between growth and stress resistance traits. On the one hand, organisms distribute energy between growth and resistance to stress. When environmental conditions are good and food is sufficient, oysters will use more energy for growth and reproductive investments; while under harsh environments or pathogen threats, oysters tend to prioritize resources for maintaining homeostasis and immune defenses, which may temporarily sacrifice growth rate. Studies have observed that some fast-growing oyster strains have relatively weak stress resistance, and it is speculated that high growth rates may come at the expense of reducing partial
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