The fatty acid composition of Octopus vulgaris paralarvae reared with live and inert food: deviation from their natural fatty acid profile

Abstract

The fatty acids of the mature ovary, late eggs and wild juveniles of Octopus vulgaris were analysed to establish, in accordance with the published data on the fatty acid composition of hatchlings, a theoretical framework of the ideal fatty acid profile, i.e. the “natural” fatty acid profile, during the early life of the species. The time course variation of the fatty acid composition of paralarvae reared in cultures fed enriched Artemia nauplii on their own, or supplemented with encapsulated microdiets, was also analysed and compared. The fatty acid composition of the cultured planktonic paralarvae was chemometrically related to that of the wild benthic juveniles by means of a multivariate discriminant analysis. Irrespective of the dietary treatment, the artificial feeding produced distinct lipid and fatty acid profiles as compared to the “natural” one. The influence of the fatty acid profile of Artemia seems clearly reflected in the cultured O. vulgaris paralarvae. The effect of the fatty acid composition of food was evident in the paralarvae after 10 days of feeding and remained essentially unchanged during the experimental period up to 30 days. The total lipid of the cultured animals increased notably, as did the levels of monounsaturated fatty acids, to the detriment of polyunsaturated fatty acids (PUFA) and, particularly, docosahexaenoic acid (DHA). Poor growth and high mortality seemed to result from a nutritional imbalance in the fatty acid profile (i.e. DHA/eicosapentaenoic acid (EPA) ratio) produced by the artificial feeding, suggesting also that the microdiet was inefficiently digested and/or assimilated. Wild juveniles tend to lose lipids as they increase in weight. Possible causes are discussed.