Key aspects of egg incubation in Patagonian red octopus (Enteroctopus megalocyathus) for cultivation purposes

Abstract

Patagonian red octopus, Enteroctopus megalocyathus, is a valuable resource of the artisanal fishery in southern Chile, however, due to overfishing the E. megalocyathus fishery was banned for 3 years in Chile, therefore its cultivation became a target for the Chilean aquaculture. The rearing of octopus paralarvae is currently the biggest bottleneck for the aquaculture of merobenthic octopus species. Besides, the embryos of Patagonian red octopus require 5 months for embryonic development, a very long period of incubation that involves high risks of contamination and detachment, therefore, little advance has been achieved in the larviculture of this species. This study represents the first investigation to evaluate the embryo viability, embryo morphometrics, embryo growth and the biochemical composition and fatty acid dynamics during early development of Patagonian red octopus under captive reproduction. The eggs obtained from broodstock conditioning were incubated under maternal care and the embryos were studied until hatching in their main morphometric and biochemical features during development. Most females showed a tending behavior of the eggs along the incubation period, losing between 40 and 100% of the eggs in the first 3 months of incubation. The results of incubation at 11 °C were successful observing the complete gastrulation, onset of organogenesis and first inversion about 48 days after spawning, the complete organogenesis and second reversion were observed about 152 days after spawning, hatching was observed 168 days after spawning without any external yolk-sac on the hatched paralarvae. During their development, embryos showed an exponential growth rate in length and weight, fueled by the protein and lipids of external yolk-sac. Metabolism of lipids showed over a 70% depletion of the saturated fatty acids (SFA), and the fatty acids 16:1, 18:2n-6, 18:3n-3 and 22:5n-3 during development. The DHA/EPA ratio remained constant throughout the incubation period. The early embryos showed a fatty acid profile dominated by both SFA and highly unsaturated fatty acids (HUFA), while the newly hatched paralarvae showed a profile dominated by HUFA.