In Vitro Testing of Alternative Synthetic and Natural Antiparasitic Compounds against the Monogenean Sparicotyle chrysophrii.

Gill monogenean Sparicotyle chrysophrii is considered the most detrimental fish parasite to the Mediterranean aquaculture. Treatment of sparicotylosis relies on frequent gill inspections correlated with the seasonal increase in seawater temperature, application of functional feeds, and treatments with formalin baths where permitted. While the latter is bound to be banned in Europe, other synthetic anthelminthics, such as praziquantel and ivermectin, are prone to induce resistance in the parasites. Therefore, we investigated, in vitro, 14 synthetic and natural compounds against adult S. chrysophrii, developing dose-response modelsm and estimated toxicity levels at 20%, 50%, and 80% parasite mortality. Bactericidal activity of target compounds was also tested in two important aquaculture bacteria; Vibrio harveyi and V. anguillarum, while their potential host toxicity was evaluated in gilthead seabream SAF-1 cell line. Synthetic compound bithionate sodium exerted the most potent toxicity against the monogenean, no host cytotoxicity, and a medium and high potency against two bacterial pathogens. In comparison, target natural compounds were approximately 20 (cedrol) or up to 154 times (camphor) less toxic for the monogenean. Rather than completely dismissing natural compounds, we suggest that their application in combination with synthetic drugs, especially if administered in the feed, might be useful in sparicotylosis treatment.

Effects of dietary Origanum vulgare on gilthead seabream (Sparus aurata L.) immune and antioxidant status.

Origanum sp. is a very common genus of aromatic plants worldwide distributed around the Mediterranean area and O. vulgare (oregano) is the most important species of this genus throughout the world. Due the known medicinal properties of oregano, the effect of diets enriched with 0% (control), 0.5% and 1% oregano leaves powder was studied on the growth, immune and antioxidant status of gilthead seabream (Sparus aurata L.). Fish fed with oregano 0.5% and 1% enriched diets improved both humoral (IgM and bactericidal activity in skin mucus and protease activity in serum) and cellular (head kidney leucocytes phagocytic ability) immunity at 15 and 30 days. Furthermore, the addition of oregano did not provoke any significant effect neither in the growth promotion nor in the liver antioxidant enzymes activity studied in the serum and skin mucus. The possibility of using O. vulgare as a functional additive to fish diet is discussed.

Carbamazepine, cadmium chloride and polybrominated diphenyl ether-47, synergistically modulate the expression of antioxidants and cell cycle biomarkers, in the marine fish cell line SAF-1.

A wide range of contaminants, industrial by-products, plastics, and pharmaceutics belonging to various categories, have been found in sea water. Although these compounds are detected at concentrations that might be considered as sub-lethal, under certain conditions they could act synergistically producing unexpected effects in term of toxicity or perturbation of biochemical markers leading to standard pathway. In this study, the Sparus aurata fibroblast cell line SAF-1, was exposed to increasing concentrations of carbamazepine (CBZ), polybrominated diphenyl ether 47 (BDE-47) and cadmium chloride (CdCl2) until 72 h, to evaluate the cytotoxicity and the expression of genes related to antioxidant defense, cell cycle and energetic balance. In general, both vitality and gene expression were affected by the exposure to the different toxicants, in terms of antioxidant defense and cell cycle control, showing the most significant effects in cells exposed to the mixture of the three compounds, respect to the single compounds separately. The synergic effect of the compounds on the analyzed biomarkers, underlie the potential negative impact of the contaminants on health of marine organisms.

Coping with exposure to hypoxia: modifications in stress parameters in gilthead seabream (Sparus aurata) fed spirulina (Arthrospira platensis) and brewer's yeast (Saccharomyces cerevisiae).

This study aimed to investigate the stress response of Sparus aurata specimens fed with nutraceutical aquafeed brewer's yeast (Saccharomyces cerevisiae) and spirulina (Arthrospira platensis). For that purpose, 96 (169.0 ± 2.8 g) animals were distributed randomly in 12 tanks (8 fish per tank, 4 replicates) and divided in 3 groups (D1, casein/gelatin, control; D2, brewer's yeast; D3, spirulina) and fed for 30 days. At the end of this period, fish from two replicates of each experimental diet were submitted to air exposure for 60 s while the fish from the other two replicates were maintained undisturbed (control). Afterwards, samples of blood, skin mucus, and head kidney were collected. The results revealed that after air exposure, cortisol, and glucose levels increased in the groups fed D1 (18.5 ± 2.6 mg/mL; 7.3 ± 0.6 mmol/L, respectively) and D2 (20.0 ± 6.2 mg/mL; 7.7 ± 0.6 mmol/L), but glucose not increased in fish fed D3 (13.7 ± 2.6 mg/mL; 5.5 ± 0.3 mmol/L). Lactate levels increased in all stressed groups, but in D1, its levels were significantly higher. After stress procedure, immunoglobulin M (IgM) levels in mucus increased only in fish fed D3 (0.1901 ± 0.0126 U/mL). Furthermore, there was a reduction in the expression of some genes involved in stress response (coxIV, prdx3, csfl-r, ucp1, and sod in fish fed D2 and D3). csf1 decreased only in stressed fish fed D2. However, cat increased in fish fed with D3. In summary, these findings points to the beneficial effects of spirulina and brewer's yeast to improve stress resistance in aquaculture practices of gilthead seabream.