International Journal of Aquaculture, 2024, Vol.14, No.3, 139-153 http://www.aquapublisher.com/index.php/ija 140 response between aquatic and terrestrial species, highlighting the role of genetic evolution in adaptation (Yang et al., 2022). Additionally, knowledge of these adaptations can inform conservation strategies, particularly as aquatic environments face increasing threats from climate change and human activities. Changes in climate and increased pollution can alter the habitats and survival conditions of aquatic species, making it essential to understand how these organisms adapt to changing conditions. For instance, marine species have been observed to shift their distributions and timing of biological events as a response to climate change, but evidence for adaptation through evolutionary processes remains limited (Miller et al., 2018). Understanding these adaptation mechanisms can guide the development of effective conservation and management strategies to protect aquatic biodiversity. This study provides a comprehensive overview of the various types of adaptations observed in aquatic species. It will delve into the molecular and genetic bases of these adaptations, exploring how these mechanisms contribute to the survival and fitness of aquatic species in their environments. Additionally, the study will discuss the implications of these adaptations in the context of environmental changes and human impacts. By highlighting recent advances in research, this study aims to deepen the understanding of the adaptive strategies employed by aquatic species to thrive in their habitats. 2 Phenotypic Plasticity 2.1 Definition and examples Phenotypic plasticity is the ability of an organism to alter its phenotype in response to changes in the environment. This section explores the definition, mechanisms, and role of phenotypic plasticity in short-term adaptation, with examples from various aquatic species. Phenotypic plasticity refers to the capacity of a single genotype to produce different phenotypes under varying environmental conditions. This adaptive flexibility can manifest in morphological, physiological, behavioral, or developmental changes, allowing organisms to better survive and reproduce in fluctuating environments. For instance, amphibious fishes exhibit significant plasticity in their ability to adapt to both terrestrial and aquatic habitats. These adaptations include changes in buoyancy control, hydration mechanisms, and respiratory function, enabling them to survive both in water and on land (Wright and Turko, 2016). Similarly, aquatic plants like Elodea nuttallii show extensive plasticity in response to varying light and nitrogen levels, which contributes to their invasive success in different water bodies (Szabó et al., 2018). 2.2 Mechanisms of phenotypic plasticity The mechanisms underlying phenotypic plasticity involve a complex interplay of genetic, molecular, and environmental factors. At the genetic level, plasticity often relies on regulatory genes that can modulate the expression of other genes in response to environmental cues. For example, the freshwater snail Radix balthica exhibits predator-induced plasticity in shell shape, driven by differential gene expression in response to the presence of predators (Hollander et al., 2017). Molecularly, these responses can involve changes in hormone levels, enzyme activities, and cellular signaling pathways that facilitate rapid phenotypic adjustments. In amphibious fishes, phenotypic plasticity allows for adjustments in metabolic processes and ion transport mechanisms, enabling them to cope with the distinct challenges of terrestrial and aquatic environments (Wright and Turko, 2016). Phenotypic plasticity also operates through developmental plasticity, where environmental conditions experienced during early life stages can influence the developmental trajectory of an organism. This is evident in frog tadpoles, which can alter their growth, development, and behavior in response to the presence of predators, enhancing their survival prospects in predator-rich environments (Van Buskirk, 2017). 2.3 Role in short-term adaptation Phenotypic plasticity plays a crucial role in the short-term adaptation of aquatic species to rapidly changing environments. By enabling immediate and reversible changes in phenotype, plasticity allows organisms to maintain functionality and fitness across a range of environmental conditions. This adaptive capacity is
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