International Journal of Aquaculture, 2025, Vol.15, No.1, 29-36 http://www.aquapublisher.com/index.php/ija 30 2 Biological Basis of Muscle Development inOxyeleotris marmorata 2.1 Stages and types of muscle growth (hyperplasia and hypertrophy) Fish are typical epigenetic and eternal animals, and their muscle development has a unique "dual mechanism". Most bone fish form new muscle fibers through the proliferation of muscle cells in the juvenile stage, while in the later stage, the growth and thickening of existing muscle fibers through hypertrophy (García-Pérez et al., 2022). In the early development stage, bamboo shoot shell fish mainly relies on satellite cells to proliferate and produce active muscle hyperplasia; as the body grows, muscle fibers mainly grow hypertrophy through protein synthesis. The combination of these two mechanisms allows fish to maintain muscle growth and growth for a long time. The muscle generation process involves the activation, proliferation and differentiation of satellite cells, as well as the regulation of myogenic regulatory factors (such as Myf5/MyoD, Myogenin, MRF4), so it has a highly complex molecular regulatory network. 2.2 Structure and functional characteristics of skeletal muscle Fish skeletal muscle tissue is mainly composed of muscle fibers and connective tissue. The muscle fiber content accounts for about 90% of muscle tissue, and the rest is a connective membrane and a small amount of fat. The muscle fibers are arranged in a layered lamellar shape, and the myomeres are separated from each other by the fascia. Fish muscles have high moisture content (≈75%), about 20% protein content, and generally have low fat content. Connective tissue (including inner membrane, outer membrane, etc.) is mainly composed of collagen, which plays an important role in the structural strength and toughness of muscle tissue (Nemova et al., 2021). The basic function of muscles is to contract movement and store energy, and its biochemical composition (protein, fat, carbohydrate ratio) directly affects the fleshy traits, such as texture and water retention (Figure 1). Figure 1 Structural characteristics of marbled sleeper (Oxyeleotris marmorata) 2.3 Muscle fiber types and their influence on flesh quality Fish muscle fibers can be divided into different types according to metabolic characteristics: fast muscle fibers (mainly glycolytic white muscles) and slow muscle fibers (oxidized red muscles rich in myoglobin). White muscle fibers are mainly responsible for rapid burst movement and are the main body of most farmed fish muscles; red muscle fibers contain hemoglobin, which supports long-lasting swimming, which is very important for fish body functions. Different fiber types have different performance in meat quality: studies have shown that in comparisons between fish, the diameter of muscle fibers is negatively correlated with the hardness of fish tissue, that is, the thinner the fibers, the more tender and firm the meat quality is usually (Wang et al., 2021). In addition, the content of collagen in muscles also has a significant impact on the hardness of meat. Several fish studies have found that collagen in muscles is positively correlated with the hardness of meat. Therefore, the type of fiber, its proportion, size and connective structure of muscle tissue together affect the texture and taste of the fish. 3 Identification and Function of Muscle Growth-Related Genes 3.1 Growth hormone/insulin-like growth factor axis (GH/IGF axis) The growth hormone (GH)-insulin-like growth factor (IGF) axis is the core endocrine pathway that regulates fish
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