Aquaculture plays a crucial role in meeting the world’s growing demand for seafood. However, challenges such as disease and environmental stressors pose significant threats to the sector’s productivity. As a potential strategy to improve the health and resilience of farmed fish, the use of natural supplements such as nucleotides has gained attention. Nucleotides are essential components of DNA and RNA and are involved in various physiological processes, including immune function. The aimed of this study was to investigate the effects of nucleotides on zebrafish (Danio rerio) early-stage development and immune system activation.
Zebrafish embryos were water-exposed to 5 different nucleotides premix concentrations (0, 5, 10, 20 and 40 mg L-1), from 24 to 120 hour post fertilization (hpf). Hatching and survival rate were daily monitored. Body length (BL), swim bladder development and yolk sac size were measured at 120 hpf, and locomotion behaviour analysed. The transgenic zebrafish line Tg(mpeg1:EGFP) was used for in vivo evaluation of macrophages activation status (fig. 1A). To this purpose confocal analysis was used for counting macrophages total number (M1, pro-inflammatory; M2, pro-healing), and their relative percentage.
Results suggest that nucleotides positively affected zebrafish embryo development, leading to improved growth parameters. Fish exposed nucleotides, showed a dose dependent effect for BL (fig. 1B) and swim bladder area. Yolk sac size was lower in all the treated groups compared to the control. The percentage of M2 macrophages was higher in fish exposed to 10 mg L-1 of nucleotides, in comparison to control, 5 mg L-1 and 40 mg L-1 (fig. 1C). This result suggests a potential role in strengthening the fish defence mechanisms. Finally, fish exposed to 10 mg L-1 of nucleotides showed the best locomotor performance, while those exposed to 40 mg L-1 showed the worst (fig. 1D). Concluding, the use of nucleotides might enhance fish growth performances, health, and resilience against biological and environmental stressors. Further research is needed to confirm their effect when nucleotides are feed included.