This work assesses the dietary use of two insect meals of Tenebrio molitor (TM) larvae reared in conventional (TM-10) or MAPs-enriched substrates (MAP-TM-10) as fish meal replacements (10%) in the diets of gilthead seabream (Sparus aurata). Fish (n=4,500; 207.19 ± 1.47 g) were divided into three groups with triplicates: Control (fed conventional diet), TM-10 and MAP-TM-10 groups.The fish were reared in floating cages for 12 weeks and The dietary effects on white blood cell ac-tivation, heat shock proteins, MAPKs, and apoptosis of the fish were evaluated. The MAP-TM-10 group exhibited the highest eosinophilic induction and plasma cells. Phosphorylated levels of p38 MAPK; p44/42 MAPK; HSP70 and HSP90 increased in the TM-10 and MAP-TM-10. In terms of apoptosis, Bax levels were lower in the TM groups compared to the Control, and the MAP-TM-10 group showed even lower levels than the TM-10 group. Bcl-2 levels increased in the TM-10 compared to the Control, and further increased in the MAP-TM-10 group. The Bax/Bcl-2 ratio, an apoptosis indicator, decreased in the TM groups, with the MAP-TM-10 group showing a further decrease compared to TM-10. These findings suggest that insects breeding substrate enriched with MAPs modulated the effect of TM on cellular stress and apoptosis.

The effect of defatted Hermetia illucens meal (HIM) dietary inclusion on growth performance, stress indicators and gut histological traits of Sparus aurata was studied. For 131 days, 312 fish were fed with one basal diet, containing fish meal as animal protein source, and three diets containing 25%, 35% and 50% HIM as a partial replacement for fishmeal. On all fish (26 fish per tank, 3 replicate tanks per diet, 78 fish per diet) the growth performance were calculated. At the end of the trial, on a subsample of 72 specimens (6 fish per tank, 3 replicate tanks per diet, 18 fish per diet), stress parameters were determined on blood samples and gut histological tract investigated. Insect meal inclusion did not affect (p > 0.05) growth performance, blood parameters, length and width of villi and goblet cell count of the posterior gut tract while, those of the anterior gut tract while increased (p < 0.05). The histological examination of the intestinal sections showed in fish fed the HIM25 and HIM50 diets, more frequent and evident morphological changes; instead, there were no substantial differences between HIM0 and HIM35 groups. In conclusion, the HIM35 was the most tolerated formulation by fish.

Sirtuins (SIRTs) are a family of evolutionarily conserved enzymes, and the aim of this study was to disclose/re-annotate uncertain paralogs in gilthead sea bream, expanding from seven to ten the repertoire of Sirts in this Perciform fish. Such gene expansion revealed up to three copies of sirt3 (sirt3.1a/sirt3.1b/sirt3.2) and two of sirt5 (sirt5a/sirt5b). Phylogenetic and synteny attempts disclosed the duplication of SIRT3/Sirt3 branch as a process shaped by the 2R whole genome duplication (WGD) at the early vertebrate evolution, with still vestiges in all living fish, and some Sarcopterygii. In gilthead sea bream and other Percomorphaceae, this duplication was accompanied by short segmental duplications of sirt3.1 (clustered to the mammalian SIRT3 ortholog), making a conserved tandem-duplicated synteny block (psmd13-sirt3.1a/b-drd4-cdhr5-ctsd). Conversely, the expansion of the Sirt5 branch was shaped by the 3R WGD as a specific event of the teleost fish lineage. Intriguingly, gene expression profiling across tissues and developmental stages highlighted a conserved high expression of sirt3.1 and sirt5a in skeletal muscle, while the duplicated sirt3.2 and sirt5b displayed an overall muscle suppression of transcriptional activity, and an enhanced expression on immune-relevant tissues and gills, respectively. Altogether offers new insights about the function, regulation, and timing of Sirt expansion.

The aim of the present study was to evaluate the effects on the presence and distribution of oxyntopeptic cells (OPs) and enteroendocrine cells (EECs) expressing GHR, NPY and SOM in the gastric mucosa of European seabass and seabream of dietary levels of bioactive peptides (BPs) obtained from salmon processing by-products (in silico approach). In this study, 27 seabass and 27 seabreams were divided into three experimental groups: a control group (CTR) fed a control diet and two groups fed different levels of BP to replace fishmeal: 5% BP (BP5%) and 10% BP (BP10%). The stomach of each fish was sampled and processed for immunohistochemistry. Some SOM, NPY and GHR-IR cells exhibited alternating “open type” and “closed type” EECs morphologies. In seabream gastric mucosa, the BP10% group (16.8 ± 7.5) showed a significant change in NPY-IR cell number compared to CTR (CTR 8.5 ± 4.8) and BP5% (BP10% vs. CTR P ≤ 0.01; BP10% vs. BP5% P ≤ 0.05). In seabream, SOM-IR cells in the BP 10% diet (16.8 ± 3.5) differed from those in CTR (12.5 ± 5) (CTR vs. BP 10% P ≤ 0.05) and BP 5% (12.9 ± 2.5) (BP 5% vs. BP 10% P ≤ 0.01). In seabass, EEC SOM-IR cells increased at 10 % BP (5.3 ± 0.7) compared to 5 % BP (4.4 ± 0.8) (5 % BP vs. 10 % BP P ≤ 0.05). The results obtained suggest that salmon BPs have a promising impact as circulating ingredients for seabass and seabream.

Cantharidin, a toxic monoterpene secreted by blister beetles, has long been used in traditional Chinese and modern medicine for its unique properties. However, despite its widespread use, its effects on fish have not been studied in depth. The aim of this study was to evaluate the potential therapeutic applications of cantharidin in fish by examining its antioxidant, hemoagglutinating, hemolytic and cytotoxic activities at different concentrations (0, 0.625, 1.25, 2.5, 5 and 10 μg mL-1) in three different cell lines. In addition, the study explored the bactericidal and bacteriostatic properties of cantharidin against various fish pathogenic bacteria. The results revealed that there were no significant differences in antioxidant, hemagglutinating or hemolytic activities between the different concentrations of cantharidin tested. However, the study found that cantharidin exhibited dose- and time-dependent cytotoxicity in sea bream (Sparus aurata) erythrocytes and in SAF-1, PLHC-1 and Hela cell lines, resulting in morphological changes indicative of apoptosis. Interestingly, the highest dose of cantharidin tested demonstrated potent bactericidal activity against four marine fish opportunistic bacteria, including Vibrio harveyi, V. anguillarum, Photobacterium damselae and Tenacibaculum maritimum, but no statistically significant changes in bacteriostatic activity were observed against any of the bacteria tested. Overall, these results provide valuable information on the potential therapeutic applications of cantharidin in fish aquaculture. Further research is needed to fully understand the mechanisms of action and to explore possible preventive uses of cantharidin in fish.