Myogenesis and muscle characteristics in rainbow trout (Oncorhynchus mykiss) reared in a photo-electrocatalytic (PEC) recirculating aquaculture system.

Research into water purification systems is pivotal for enhancing the sustainability of the recirculating aquaculture system (RAS). This study has pioneered the development of a novel tool utilizing photoelectrocatalysis (PEC). The innovation builds upon the conventional UV-filtration system by integrating it with biofiltration, thereby augmenting water purification capabilities. Fish farmed in RAS may encounter elevated ammonia, nitrates, and nitrites, leading to toxicity and adverse effects on health and growth. Our study aims to explore the effects of muscle development in rainbow trout farming, with fish reared at 15 kg/m2 density in a control group (CTR) or a PEC group (T) in the grow-out phase (100g-160g). Muscle samples were obtained from the lateral line (red muscle) and anterior dorsal musculature (white muscle) for morpho-functional studies. Periodic Acid-Schiff (PAS) assay was employed to assess glycogen content in white muscle fibers, while immunofluorescence staining was conducted to identify muscle fiber types: type I for slow-twitch/red and type IIb for fast-twitch/white fibers. Moreover, molecular analyses were performed to evaluate genes involved in myogenesis (Myod, Myog Myf5, or myostatin) to assess muscle health. Finally, computed tomography (CT) was useful to evaluate the physical density of skeletal muscle. Morphological analyses revealed no abnormalities in muscle structure, and neither did the characterization of fibers, the myogenic process, nor the density of skeletal muscle in CT show significant differences between the groups. Water parameters tested during the whole study revealed no significant difference except for nitrates which were lower in the PEC (122.211 mg/L vs. 108.510 mg/L; p < 0.001). These findings suggest that the PEC system is safe and does not adversely affect muscle structure. However, further evaluation of additional parameters related to both water quality and fish health is warranted.