Macroalgae-enriched diet protects gilthead seabream (Sparus aurata) against erythrocyte population instability and chromosomal damage induced by aqua-medicines

The incorporation of macroalgae on aquafeeds has been suggested to increase fish growth and organoleptic characteristics. Moreover, the potential of macroalgae to strengthen fish capacity to cope with different stressors is a challenging topic in the field of applied phycology. The adverse side effects of aqua-medicines, combined with the hypothesis that a macroalgae-enriched diet can minimize that impact, are the starting point for the present study. Hence, a mix of Ulva rigida, Fucus vesiculosus and Gracilaria gracilis was incorporated (5%) in the gilthead seabream (Sparus aurata) diet, to evaluate a possible protection against the chromosomal damage (measured as erythrocytic nuclear abnormalities) induced by the antibiotic oxytetracycline and the antiparasitic formalin as well as by the model genotoxicant cyclophosphamide. A 60-day differential dietary background was implemented (one fish group fed with standard diet and other with macroalgae-supplemented diet), after which fish were challenged by oxytetracycline, formalin and cyclophosphamide, and appraisals carried out 4 and 18 days later. To shed light on the modulation of the erythrocytic population dynamics, the erythrocyte maturity index was assessed. Oxytetracycline and formalin displayed a chromosome-damaging potential that remained for 18 days. The macroalgae-enriched diet evidenced a solid genoprotection against the three agents, revealing a broad-spectrum action. Oxytetracycline and formalin induced an erythrocyte population instability (translated into an aging effect), counteracted by algae supplementation, which seems to convey erythropoiesis promoting factors. Overall, the benefits given by the algae supplementation recommend its adoption within a framework of sustainable aquaculture practices, namely as a prophylactic measure to mitigate productivity losses when oxytetracycline and formalin are used.