, Volume 146, Issue 4, pp 739-751
Date: 10 Nov 2004

Biochemical composition of cephalopods with different life strategies, with special reference to a giant squid, Architeuthis sp.

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Abstract

The present study is a comprehensive comparison of the biochemical composition (protein, lipid, glycogen and cholesterol contents, and amino acid and fatty acid profiles) of 14 species of cephalopods with different life strategies (benthic, nektobenthic, benthopelagic and pelagic) in distinct habitats (neritic, demersal, oceanic and deep sea), with special emphasis placed on a male Architeuthis sp. The giant squid showed a significantly lower protein and total amino acid content in the gonad and digestive gland. The major essential amino acids were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and proline. The benthopelagic cirrate octopus Opisthoteuthis sp. showed a lower content of these nitrogen compounds in the muscle. In respect to lipid and fatty acid contents, the giant squid showed the highest values in the gonad and digestive gland and the lowest in the muscle. Most of saturated fatty acid content was presented as 16:0; monounsaturated fatty acid content, as 18:1 and 20:1; and polyunsaturated fatty acid content, as 20:4n-6, 20:5n-3 and 22:6n-3. The highest cholesterol content in the gonad was detected in Opisthoteuthis sp. and Architeuthis sp.; in the digestive gland. in Todarodes sagittatus; and in the muscle, in Sepia elegans. The highest glycogen value in the gonad was detected in Octopus vulgaris; in the digestive gland and muscle, the highest values were attained in Opisthoteuthis sp. The relationships between life strategies and biochemical composition were investigated and principal component analysis (PCA) was performed. The different cephalopod life strategies could be well separated on the basis of the first two principal components. The nektobenthic and pelagic strategies were clearly separated from the benthic, suggesting that these groups of species are characterized by lower lipid content and higher protein content in the gonad. A rather similar life-strategy distinction was obtained for the digestive gland. The benthopelagic strategy was also well separated from benthic and pelagic strategies and from Architeuthis sp. In the muscle, the results indicated lower nitrogen and carbon compound contents in Architeuthis sp. and Opisthoteuthis sp. The environmental conditions that possibly explain the Architeuthis sp. stranding, the relationships between biochemical compositions and the life strategies of the different cephalopod species studied are discussed.

Communicated by S.A. Poulet, Roscoff