Squalene content and neutral lipis composition of Livers from Deep-sea sharks caught in Tasmanian waters

Abstract

Deep-sea sharks (mainly dogfish) are a significant by-catch of trawls for the deep-water fish orange roughy (Hoplostethus atlanticus). To test whether the livers of these sharks might be a source of commerically valuable squalene and other lipids, 16 sharks of 8 species were collected from Tasmanian waters at depths of 700-1200 m during research cruise S02/88 of FRV Soela. The sharks were Centroscyrnnus crepidater (longnose velvet dogfish), Centroscyrnnus owstoni (Owston's dogfish), Centroscyrnnus coelolepis (Portuguese dogfish), Deania calcea (shovelnose dogfish), Etmopterus baxteri (Baxter's dogfish), Etmopterus sp. nov. (unnamed dwarf dogfish), Dalatias licha (kitefin or seal shark) and Centrophorus squarnosus (leafscale gulper shark). Squalene content, triacylglycerols, diacylglyceryl ethers, total fatty acids, pristane and other lipids were analysed by capillary gas chromatography and thin-layer chromatography-flame ionization detection. The livers contained high levels of squalene (15-69% by weight), except for the liver of C. squarnosus (I%), which had an unusually high amount of diacylglyceryl ethers (79%). Triacylglycerol and diacylglyceryl ether contents in the livers ranged from 1 to 26% and from 7 to 79% by weight respectively. The C19 isoprenoid alkane pristane was a minor constituent in all samples (0.01-0.56% by weight of liver). The three major esterified fatty acids in all samples were palmitic (16:0), oleic [18: 1 (n - 9)] and eicosa-11-enoic [20: 1 (n - 9)] fatty acids. Polyunsaturated fatty acids were minor constituents. These data indicate that shark livers could provide a profitable by-catch from deep-water trawls, but it is unlikely that shark could form the basis for a target fishery due to their susceptibility to overfishing.

Lipids and buoyancy in Southern Ocean pteropods

“…DAGE is an abundant component of liver oil of certain shark species (22). Plunket shark (Centroscymnus plunketi), Pacific sleeper shark (Somniosus pacificus) (23), and the leafscale gulper shark (Centrophorus squamosus) (24) have livers rich in DAGE. The liver of many of these sharks is over 50% oil; in some it is over 80% (25).…”

Ether lipids

“…For instance, some shark species of the Squaliformes (dogfish sharks) order possess liver to body weight ratios of about 20% and oil to liver weight ratios ranging from 65% for Centroscymnus owstoni (Owstonís dogfish) (Wetherbee and Nichols, 2000) to 86% for Centrophorus squamosus (Leafscale gulper shark) (Deprez et al, 1990). Hitherto, the highest DAGE amount reported in the liver oil of a chondrichthyan is from the Squaliforme Scymnodon plunketi, which contained 89% DAGE, 10% triacylglycerol and none squalene in its liver oil (Wetherbee and Nichols, 2000).…”

“…Hitherto, the highest DAGE amount reported in the liver oil of a chondrichthyan is from the Squaliforme Scymnodon plunketi, which contained 89% DAGE, 10% triacylglycerol and none squalene in its liver oil (Wetherbee and Nichols, 2000). Table 1 DAGE and TAG % in the liver oil of S. acanthias from different places: (a) Kang et al (1998), (b) Malins et al (1965), (c) Wetherbee and Nichols (2000 The lipid compositions of some deep-sea Squaliformes from Australian, New Zealand and Tasmaninan waters are well documented and a compilation of the major lipids in their liver oils shows the mean percentages of DAGE (24 ± 7%), squalene (65 ± 11%) and TAG (10 ± 5%) for the following species: Centroscymnus crepidater, Centroscymnus owstoni, Dalatias licha, Deania calcea, Etmopterus granulosus, Centrophorus crepidater, Centrophorus scalpratus, Centroscymnus coelolepis, and Etmopterus baxteri (Bakes and Nichols, 1995;Deprez et al, 1990;Wetherbee and Nichols, 2000). High DAGE:TAG ratios are relevant for industry since in the process of DAGE extraction and refinement for health supplements DAGE and TAG are usually not separated.…”

NMR determination of site‐specific deuterium distribution (SNIF‐NMR) in squalene from different sources

“…The liver of the shark Centroforus granulosus is particularly rich in squalene, 18 so it was possible to extract it as raw oil by simple mild pressing. The oil obtained was then centrifuged at 747 g for 30 min to eliminate tissue residuals and analysed by high-performance liquid chromatography (HPLC) to determine its composition.…”