Does the trophic habitat influence the biochemical quality of the gonad of Octopus vulgaris? Stable isotopes and lipid class contents as bio-indicators of different life-cycle strategies

This study aims to test whether environmental conditions including the trophic habitat and diet impact the biochemical composition of storage organs and affect the nutritional quality of eggs of Octopus vulgaris. Trophic habitat and gonad quality of neighbouring populations off the Portuguese coast, subject to different oceanographic regimes, were compared using the digestive gland and beaks as recorders of trophic and habitat preferences, and gonads as indicators of egg quality. Cholesterol, phospholipids and triacylglycerol content, essential fatty acid (EFA) profile of the digestive gland and stable isotopes, δ15N and δ13C, in the buccal mass flesh and beaks were indicators of the differences in the trophic habitat between populations. For gonad quality, the same bio-indicators were used to identify differences with maturation. The study shows that, although diet influences the EFA profile of the gonads to a certain degree, the main lipid content, phospholipids and cholesterol content in the gonads are not influenced by habitat conditions. This, therefore, suggests that O. vulgaris is able to influence the quality of egg content independent of diet. The species is believed to be an income breeder which attains maturity upon reaching a sufficient condition level, then channelling energy directly from food to gonad development.