International Journal of Aquaculture, 2024, Vol.14, No.2, 81-90 http://www.aquapublisher.com/index.php/ija 83 3.3 Cellular and molecular processes At the cellular and molecular levels, largemouth bass exhibit various adaptive mechanisms to environmental stressors. For instance, miRNAs play a significant role in regulating gene expression related to hypoxic stress. Differential expression of miRNAs in the liver under hypoxic conditions has been linked to the VEGF, MAPK, and phosphatidylinositol signaling pathways, which are crucial for cellular responses to low oxygen levels (Sun et al., 2020). Additionally, metabolic adaptation to dietary changes, such as high-starch diets, involves the upregulation of genes related to bile acid synthesis, inflammation, and energy metabolism, indicating a state of 'self-repair' in largemouth bass (Chen et al., 2022). These cellular and molecular processes are essential for maintaining homeostasis and promoting growth and development in varying environmental conditions. 4 Environmental Adaptation Mechanisms 4.1 Physiological adaptations Largemouth bass (Micropterus salmoides) exhibit several physiological adaptations that enable them to thrive in diverse environmental conditions. One significant adaptation is their ability to regulate ionic balance in varying salinity levels. The expansion of the claudin gene family, which is crucial for cell tight junctions and osmotic homeostasis, plays a vital role in this process. This gene family has 27 members and 68 copies in largemouth bass, facilitating their adaptation to both fresh and brackish water environments (Sun et al., 2020). Additionally, largemouth bass can adapt to high environmental ammonia (HEA) by modulating their ammonia excretion rates and upregulating specific mRNA expressions, such as Rhesus glycoproteins, which aid in ammonia excretion. Furthermore, they exhibit metabolic adaptations to dietary changes, such as high-starch diets, by restoring metabolic functions through inflammation, bile acid synthesis, and energy metabolism (Chen et al., 2022). 4.2 Behavioral adaptations Behavioral adaptations in largemouth bass are less documented compared to physiological and genetic adaptations. However, their ability to modify feeding habits in response to environmental changes is notable. For instance, largemouth bass have shown adaptability to formulated feeds instead of traditional forage fish diets, which is crucial for aquaculture sustainability. This dietary transition is supported by genetic markers associated with food habit domestication traits (Cui et al., 2023). Additionally, largemouth bass exhibit changes in activity levels and metabolic rates in response to hypoxic conditions, which helps them conserve energy and survive in low-oxygen environments (Yang et al., 2019). 4.3 Genetic basis of adaptation The genetic basis of adaptation in largemouth bass is underpinned by several genomic and transcriptomic modifications. Whole-genome resequencing has revealed selective sweep regions and candidate genes associated with growth, early development, and immune traits, which are crucial for their adaptation to various environmental pressures (Sun et al., 2023). The identification of sex-specific markers and the XX/XY sex determination system also highlights the genetic mechanisms underlying sex dimorphism and potential for selective breeding (Du et al., 2021). Moreover, the response to environmental contaminants, such as endocrine disruptors, involves specific gene expression changes that can be used as biomarkers for environmental stress (Sanchez et al., 2009; Basili et al., 2018). These genetic insights provide a comprehensive understanding of the adaptive mechanisms in largemouth bass, facilitating their conservation and breeding programs. 5 Integration of Genomic and Developmental Data 5.1 Combined genomic and developmental studies The integration of genomic and developmental data in largemouth bass (Micropterus salmoides) has provided significant insights into their adaptive mechanisms to environmental stressors. For instance, studies have shown that exposure to high environmental ammonia (HEA) triggers a series of physiological and molecular responses. These responses include changes in oxygen consumption, ion regulation, and the expression of specific genes such as Rhesus glycoproteins, which play a crucial role in ammonia excretion (Egnew et al., 2019). Similarly, the liver proteome response to various environmental contaminants has been analyzed to identify potential biomarkers, revealing alterations in proteins associated with cellular ion homeostasis, oxidative stress, and energy production
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