Co-supply with marine crustacean to enriched Artemia as food for the Patagonian red octopus (Enteroctopus megalocyathus) paralarvae

One of the most sensitive problems in the Patagonian red octopus (Enteroctopus megalocyathus) aquaculture is the high mortality of the paralarvae stage. Paralarvae are active hunters, and the enriched Artemia is the most traditional food for this species until 60 days after hatching (DAH). Then, the pre-settlement behavior appears, and co-feeding with juvenile sea crabs is initiated for another 30 days up to 90 DAH when settlement occurs and the paralarvae stage ends. Therefore, the present study aimed to investigate the effect of marine juvenile crabs on the Patagonian red octopus paralarva's feeding history before the pre-settlement stage. Early paralarvae (1 to 15 DAH) were fed two diets: only enriched Artemia (A) or enriched Artemia plus juvenile crab (AC). At 15 DAH, one-half of each group was exchanged with the opposite treatment during the following 35 days of the experimental period. An experimental design resulted in four combinations of early and late diets, A-A, A-AC, AC-A, and AC-AC. The overall performance and the expression of genes related to fatty acid biosynthesis, antioxidant defense system, and stress response were evaluated in paralarvae at 15 and 50 DAH. Besides, fatty acids and amino acids were compared between the four combinations at 50 DAH. At 15 DAH, the main differences were the highest length and growth rate in paralarvae-fed AC. At 50 DAH, after 35 days fed the four combinations of early-late diets, no differences were detected in SGR. In contrast, those paralarvae of AC-A and AC-AC triplicate their survival upon A-A and A-AC. Paralarvae from the A-A combination resulted in the lowest protein content, highest ash, and the highest expression of FADS5. In comparison, paralarvae from the A-AC combination resulted in the highest 18:3n-3 and PUFA n-6 and the lowest amount of free serine. Precisely the contrary to paralarvae fed AC-AC. Therefore, the relevance of the first feeding until 15 DAH upon further paralarvae development is discussed, and how co-feeding with juvenile crabs improves the overall performance compared to using only enriched Artemia.