Lipids of Hoplostethus atlanticus and H. mediterraneus (Beryciformes: Trachichthyidae) from deep water to the west of Britain

Abstract

Lipid analyses were carried out on Hoplostethus atlanticus and H. mediterraneus caught in 1300 to 1330 m and 725 to 740 m of water, respectively, on the Porcupine Bank off the west coast of Ireland in March 1982, with a view to furthering our understanding of the distribution of wax esters in mid- and deep-water fish. Wax esters were major lipids in the oil-rich muscle, belly flap, liver and pyloric caeca of H. atlanticus and large amounts of wax esters were also present in its swim bladder and cranial cavity. H. mediterraneus did not have oil in its swim bladder and the lipid in its cranial cavity was mainly triacylglycerols. The muscle, belly flap and liver of H. mediterraneus had lower percentages of lipid than the corresponding tissues from H. atlanticus and the major lipid present was triacylglycerols. However, wax esters were present in the testis of H. mediterraneus and significant amounts were also present in its liver. The triacylglycerols of the liver and cranial cavity of H. mediterraneus contained substantial amounts of 20:1 (n-9) and 22:1 (n-11) fatty acids. The wax esters of all tissues of H. atlanticus were very rich in 18:1 (n-9), 20:1 (n-9) and 22:1 (n-11) fatty acids. The results are discussed with respect to the origin and abundance of 20:1 and 22:1 fatty alcohols in pelagic food webs.