One of the most sensitive problems in the Patagonian red octopus (Enteroctopus megalocyathus) aquaculture, is the high mortality of paralarvae. Paralarvae are active hunters being highly selective until they reach the juvenile stage, around 90 to 120 days after hatching (DAH). Artemia is the food provided to paralarvae, with enrichment practices to provide better nutrients like essential amino acids and fatty acids.
The aim of the present study was to investigate the mortality preventive effect of diet in paralarvae between 15 and 50 DAH (i.e. from the maternal reserves have been depleted until the time before the benthic settlement) both through using juvenile crabs to co-feeding and varying diet of the previous feeding period. The growth, biochemical composition, and the expression of genes related with fatty acid biosynthesis, antioxidant defense system and stress response in paralarvae were evaluated after a experimental period of 35 days. To obtain paralarvae of 15 DAH two diets were used: only enriched Artemia (A), or enriched Artemia plus crab (AC), when paralarvae reached 15 DAH, each group was divided in two new groups that were fed until 50 DAH with enriched Artemia with or without co-feeding with crabs. Treatment names indicated the diet before and after 15 DAH, as follows: A-A, A-AC, AC-A, and AC-AC.
No differences were detected in weight growth, whereas those paralarvae fed A-A and AC-A, resulted in longer length. On the contrary, the highest survival was observed with both groups fed with crab juveniles at initial diet, with 40.5% for AC-AC, followed by AC-A with 34.8%, far higher than those A-A and A-AC (9.5 and 16.2%, respectively). Also, a trend towards a higher value in AL/ML ratio, highest values of 18:0, and the absence of 20:4n-6, were observed in paralarvae fed A-AC and AC-AC, without effect of the initial diet and without interaction between the diets of both periods. Of the genes analyzed, only the expression of the stress protein HsP70 showed a trend to higher values in paralarvae fed in the A-A the same with the highest mortality. It is discussed how co-feeding with juvenile crab resulting in an improvement compared to the use of pure enriched Artemia.
Fundings: FONDECYT 1200668