Characterization of Lipids in Myctophid Fish in the Subarctic and Tropical Pacific Ocean

Abstract

Lipids in 26 samples including the 20 species of myctophid fishes (Family Myctophidae) caught in the western subarctic and tropical Pacific Ocean were characterized. Myctophid fishes contained lipids at the level of 0.5 to 21.7% and were classified into three groups by lipid class composition, i.e., triglyceride-rich (5 species), wax ester-rich (3 species) and phospholipid-rich (12 species) groups. No fish which is rich in both triglycerides and wax esters was observed in the present study. The triglyceride-rich and wax ester-rich groups were found in the western subarctic Pacific, i.e., the Oyashio species, while the phospholipid-rich group with low-lipid content was found in the tropical species, i.e., the Equatorial and Central Water species. Three species, Stenobrachius leucopsarus, Lampanyctus regalis and Stenobrachius nannochir, contained wax esters with 30 to 44 carbon chain lengths as the major lipids, always accounting for more than 90% of total lipids. The main alcohol moieties of wax esters were 16:0, 20:1 and 22:1, while oleic acid (18:1n-9) and other monoenoic acids were predominantly fatty acids. Lipid composition analyses suggested the tendency that wax esters are rich in non-migratory or partly-migratory species.