Exploring the Antioxidant and Genoprotective Potential of Salicornia ramosissima Incorporation in the Diet of the European Seabass (Dicentrarchus labrax)

Abstract

The identification of novel feed materials as a source of functional ingredients is a topical priority in the finfish aquaculture sector. Due to the agrotechnical practices associated and phytochemical profiling, halophytes emerge as a new source of feedstuff for aquafeeds, with the potential to boost productivity and environmental sustainability. Therefore, the present study aimed to assess the potential of Salicornia ramosissima incorporation (2.5, 5, and 10%), for 2 months, in the diet of juvenile European seabass, seeking antioxidant (in the liver, gills, and blood) and genoprotective (DNA and chromosomal integrity in blood) benefits. Halophyte inclusion showed no impairments on growth performance. Moreover, a tissue-specific antioxidant improvement was apparent, namely through the GSH-related defense subsystem, but revealing multiple and complex mechanisms. A genotoxic trigger (regarded as a pro-genoprotective mechanism) was identified in the first month of supplementation. A clear protection of DNA integrity was detected in the second month, for all the supplementation levels (and the most prominent melioration at 10%). Overall, these results pointed out a functionality of S. ramosissima-supplemented diets and a promising way to improve aquaculture practices, also unraveling a complementary novel, low-value raw material, and a path to its valorization.

Keywords: DNA integrity; fish feedstuff; functional feed; halophytes; sustainable aquaculture.

Figure 1

Peripheral erythrocytes of Dicentrarchus labrax. (Left): blood smear (Giemsa stain) showing erythrocytes in different stages of maturation. (Right): representation of erythrocytes (with nuclear normal shape) elucidating measurements performed for the calculation of the erythrocyte maturity index (EMI), viz. minor axis of the nucleus (A) and major axis of the cell (B). In both images, erythrocytes in earlier (1) and later (2) maturity stages are represented.

Figure 2

Mean values of oxidative stress parameters in the liver, namely (A) superoxide dismutase (SOD), (B) catalase (CAT), (C) glutathione peroxidase (GPx), (D) glutathione-S-transferase (GST), (E) glutathione reductase (GR) activities, and (F) total glutathione content (GSHt), as well as (G) lipid peroxidation (LPO), following 1 (light green) and 2 months (dark green) of dietary supplementation. Experimental groups concern: control (C), fed with standard feed, and Salicornia-supplemented diets (S2.5, S5, and S10, corresponding to 2.5%, 5%, and 10% supplementation, respectively). Bars represent standard errors. Different letters correspond to statistically significant differences (p < 0.05), within the same trial duration (lowercase letters for 2 months).

Figure 3

Mean values of oxidative stress parameters in the gills, namely (A) superoxide dismutase (SOD), (B) catalase (CAT), (C) glutathione peroxidase (GPx), (D) glutathione-S-transferase (GST) activities, (E) glutathione reductase, and (F) total glutathione content (GSHt), as well as (G) lipid peroxidation (LPO), following 1 (light green) and 2 months (dark green) of dietary supplementation. Experimental groups concern: control (C), fed with standard feed, and Salicornia-supplemented diets (S2.5, S5, and S10, corresponding to 2.5%, 5%, and 10% supplementation, respectively). Bars represent standard errors. Different letters correspond to statistically significant differences (p < 0.05), within the same trial duration (capital letters for 1 month; lowercase letters for 2 months).

Figure 4

Mean values of oxidative stress parameters in the blood, namely (A) superoxide dismutase (SOD), (B) catalase (CAT), (C) glutathione peroxidase (GPx), (D) glutathione-S-transferase (GST) activities, and (E) total glutathione content (GSHt), as well as (F) lipid peroxidation (LPO), following 1 (light green) and 2 months (dark green) of dietary supplementation. Experimental groups concern: control (C), fed with standard feed, and Salicornia-supplemented diets (S2.5, S5, and S10, corresponding to 2.5%, 5%, and 10% supplementation, respectively). Bars represent standard errors. Different letters correspond to statistically significant differences (p < 0.05), within the same trial duration (capital letters for 1 month; lowercase letters for 2 months).

Figure 5

DNA and chromosomal damage in blood cells of the European seabass. DNA strand breaks measured by the comet assay (A), and expressed as percentages of DNA in the tail, and erythrocytic nuclear abnormalities frequency (‰) (B), following 1 (light green) and 2 months (dark green) of dietary supplementation. Experimental groups concern: control (C), fed with standard feed, and Salicornia-supplemented diets (S2.5, S5, and S10, corresponding to 2.5%, 5%, and 10% supplementation, respectively). Bars represent standard errors. Different letters correspond to statistically significant differences (p < 0.05), within the same trial duration (capital letters for 1 month; lowercase letters for 2 months).

Figure 6

Representation of frequency (%) of classes 1 to 7 of the erythrocyte maturity index (EMI) evaluated in peripheral erythrocytes, following 1 (top-left) and 2 months (bottom) of dietary supplementation, and class 5 (top-right) in the first month. Experimental groups concern: control (C), fed with standard feed, and Salicornia-supplemented diets (S2.5, S5, and S10, corresponding to 2.5%, 5%, and 10% supplementation, respectively). Bars represent standard errors. Different lowercase letters correspond to statistically significant differences (p < 0.05).