The fusion of myoblasts is a crucial stage in the growth and development of skeletal muscle. Myomaker is an important myoblast fusion factor that plays a crucial role in regulating myoblast fusion. However, the function of Myomaker in economic fish during posthatching has been poorly studied. In this study, we found that the expression of Myomaker in the fast muscle of Chinese perch (Siniperca chuatsi) was higher than that in other tissues. To determine the function of Myomaker in fast muscle, Myomaker-siRNA was used to knockdown Myomaker in Chinese perch and the effect on muscle growth was determined. The results showed that the growth of Chinese perch was significantly decreased in the Myomaker-siRNA group. Furthermore, both the diameter of muscle fibers and the number of nuclei in single muscle fibers were significantly reduced in the Myomaker-siRNA group, whereas there was no significant difference in the number of BrdU-positive cells (proliferating cells) between the control and the Myomaker-siRNA groups. Together, these findings indicate that Myomaker may regulate growth of fast muscle in Chinese perch juveniles by promoting myoblast fusion rather than proliferation.

Freezing is the most commonly used preservation method for aquatic products, but the freeze–thaw cycle leads to the formation and growth of ice crystals, which seriously affects the quality of fish. This study evaluated the effect of dietary supplementation with theabrownins (TBs) on the quality attributes of grass carp (Ctenopharyngodon idella) muscle following freeze–thaw treatment. We examined changes in textural properties, ice crystal morphology and metabolomic profiles in response to TBs inclusion in feed. The results indicated that feeding TBs at 0.02% and 0.06% levels significantly improved the chewiness and cohesiveness of grass carp muscle. Histological analysis revealed that TB-containing feed effectively inhibited ice crystal growth, leading to smaller and more uniform ice crystals, thereby mitigating structural damage to muscle tissue. Metabolomic analysis identified distinct metabolite profile differences between the treatment groups and the control group, with both LTB (0.02% TBs) and HTB (0.06% TBs) groups showing significant upregulation of esters and aromatic compounds compared to the control group. The present study demonstrates that TBs, as a natural feed additive, can enhance the freeze–thaw tolerance of grass carp muscle by modulating ice crystal formation and influencing muscle metabolism. This study provides important insights and practical implications for developing novel strategies to improve the quality of frozen aquatic products.

Twist2 plays a pivotal regulatory role in the growth of skeletal muscle across various organisms. Nonetheless, the specific mechanism by which Twist2 governs skeletal muscle function in fish, particularly in the economically significant Chinese perch (Siniperca chuatsi), remains unclear. Within the muscle injury model in Chinese perch, we observed that Twist2 expression was upregulated during the repair phase of fast muscle tissue, exhibiting an expression pattern analogous to that of Pax7. Following the knockdown of Twist2 using Twist2-specific in vivo-siRNA in fast muscle tissues, the expression of myogenic regulatory factors (MRFs) and Myomaker was significantly reduced in the Twist2-siRNA-treated group compared with the control group, whereas no significant differences were observed for Pax3 and Pax7. Furthermore, the diameter of myofibers and the number of nuclei in single myofibers were reduced, and concurrently, the number of BrdU-positive cells (proliferating cells) was significantly reduced in the Twist2-siRNA-treated group. Taken together, this study demonstrates that Twist2 promotes myoblast proliferation and fusion, thereby regulating fast muscle growth in juvenile Chinese perch. These findings provide a clear direction for further exploration of molecular mechanisms underlying skeletal muscle growth in economic fish species.

Sperm cryopreservation is crucial for artificial propagation and the long-term preservation of valuable germplasm resources. This study aimed to establish an effective ultra-low temperature sperm cryopreservation protocol for Hefang bream (HFB), a novel hybrid bream variety developed through distant hybridization between blunt snout bream (Megalobrama amblycephala) and topmouth culter (Culter alburnus) followed by two rounds of backcrossing. Different combinations of extenders and cryoprotectants were evaluated based on post-thaw sperm motility and motion parameters to identify the optimal cryoprotective formulation for HFB sperm, with untreated fresh sperm as the control. Fresh sperm exhibited a total motility (MOT) of 98.87 ± 1.40%, curvilinear velocity (VCL) of 118.87 ± 5.38 μm/s, straight-line velocity (VSL) of 86.18 ± 5.67 μm/s, and average path velocity (VAP) of 107.48 ± 4.23 μm/s. The optimal formulation consisted of D15 extender (composed of 8 g/L NaCl, 0.5 g/L KCl and 15 g/L glucose) supplemented with 10% dimethyl sulfoxide (DMSO). Using a fresh sperm-to-cryoprotective medium ratio of 1:5 and a stepwise cooling procedure, post-thaw MOT, VCL, VSL, and VAP were 43.77 ± 13.85%, 37.54 ± 3.06 μm/s, 29.82 ± 1.98 μm/s, and 31.99 ± 2.14 μm/s, respectively. Further analyses revealed that the plasma membrane integrity (PMI), DNA integrity (DI) and mitochondrial activity (MA) of cryopreserved sperm were 43.40 ± 2.01%, 57.10 ± 4.79%, and 42.00 ± 1.65%, respectively, all of which were significantly lower than those of fresh sperm (p < 0.05). Ultrastructural analyses using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that cryopreserved spermatozoa exhibited structural abnormalities, including plasma membrane disruption, flagellar fragmentation, and mitochondrial damage. Artificial insemination experiments showed that the fertilization and hatching rates of the cryopreserved sperm group were 55.10 ± 3.30% and 81.50 ± 3.29%, respectively, indicating that the established protocol could effectively support artificial reproduction in HFB. Furthermore, proteomic analysis was performed to investigate cryopreservation-induced molecular damage, identifying 7 cryopreservation-associated leakage proteins that were mainly enriched in pathways related to energy metabolism, cytoskeletal organization, and oxidative stress response. This study establishes an effective sperm cryopreservation protocol for HFB and provides insights into the cellular and molecular mechanisms underlying cryopreservation-induced sperm damage, offering a valuable reference for the development of sperm cryopreservation technologies in other economically important fish species.