Dietary Phospholipids Enhance Growth Performance and Modulate Cold Tolerance in Meagre (Argyrosomus regius) Juveniles

Abstract

Meagre (Argyrosomus regius) is a fast-growing species currently produced in aquaculture. This species is highly sensitive to low environmental temperatures which results in high mortality events during production cycles. In this study, the effects of dietary phospholipids (PLs) on growth and cold tolerance were evaluated. For this purpose, control (CTRL) and PL-enriched diets (three-fold higher levels than CTRL) were supplied to meagre juveniles (12.9 ± 2.5g) for 60 days, and growth was determined using a longitudinal approach. Weight gaining and SGR reduction were significantly different between dietary treatments. Animals fed with the PL-enriched diet were 4.1% heavier and grew 3.2% faster than those fed with the CTRL diet. Survival was higher than 98% in both groups. After finishing the growth trial, animals were submitted to two cold challenges and cold tolerance was evaluated as temperature at death (Tdeath), risk to death and lethal doses (LD) 50 and 90 using the cumulative degree cooling hours 6 h (CD6H). Tdeath ranged between 7.54 and 7.91 °C without statistical differences between dietary treatments. However, risk to death was significantly smaller (0.91-fold lower) and LD50 and LD90 were higher in animals fed with the PL-enriched than those supplied the CTRL diet. To assess the fatty acid (FA) composition of liver and brain in animals fed both diets after a cold challenge, FA profiles were determined in juveniles maintained at 14 °C and challenged at 7 °C. FA amounts increased in the liver of animals challenged at 7 °C. In contrast, several FAs reduced their levels in the PL-enriched diet with respect to CTRL indicating that these animals were able to mobilize efficiently lipids from this organ mitigating the negative effects of lipid accumulation during the cold challenge. In brain, the PL-enriched diet increased DHA level during the cold shock indicating a role in maintaining of brain functions. These results open a new research line that could improve the cold tolerance of meagre through dietary supplementation before winter.

Thyroid Hormones in Hemolymph of Red King Crabs from the Barents Sea

“…Opportunities include further development of the aquaculture sector [27]. Coastal sites of the Kola Peninsula have favorable environmental conditions for invertebrate aquaculture [27,52], but profitable aquaculture cannot be organized without excellent knowledge regarding the ecology and physiology of target organisms [39,53,54]. The red king crab is a slow-growing species reaching the commercial size of 150 mm carapace width (or 137 mm carapace length) after 10 years of growth.…”

Fatty Acid Profile and Escherichia coli and Salmonella sp. Load of Wild-Caught Seaweed Fly Fucellia maritima (Haliday, 1838) (Diptera: Anthomyiidae)

“…In conclusion, the FA profile of this seaweed fly in the wild presents many biomolecules of interest for the formulation of aquafeeds, whether for the maintenance of optimal growth of aquatic animals or the overall health of farmed fish, considering this species’ high level of C20:5 n-3 , an essential FA for optimal fish and shrimp growth. Moreover, F. maritima contains highly valuable PLs, which are important supplements for aquafeed, especially in early life stages [ 58 , 59 ]. Additionally, these flies display lower counts of human pathogenic bacteria when compared to other insect species already used in commercial applications, and their use may contribute towards the diversification of insect species production for feed, thus enhancing the resilience of this young industry [ 8 ].…”