Lipids and their Role in the Metabolism of Semen 125 



When air-dried salmon roe is ground and extracted with pentane 

 in a Soxhlet apparatus, a yellow oil is obtained which is practically 

 free from phospholipids; it requires further treatment with ethanol 

 or methanol for the phospholipids to be extracted from the sperm. 

 In this way, for example, 12-5% glyceride in the oily fraction, and 

 6-2% phospholipid in the alcoholic fraction, was obtained from the 

 roe of the sockeye salmon, Oncorhynchus nerka (Halpern, 1945). On 

 the basis of this observation, it has been suggested that the phos- 

 pholipids occur in the spermatozoa in a firmly bound state, pre- 

 sumably in the form of lipoproteins. A substantial portion of the 

 unsaponifiable material extracted from fish sperm by fat solvents 

 consists of cholesterol which accounts, on the average, for 2-2% 

 of dried fish spermatozoa (Schmidt-Nielsen and Sundsvold, 1943). 



The high content of lipids in spermatozoa is equally characteristic 

 for fishes as for other animals. Sea-urchin spermatozoa are well 

 known to contain a large reserve of lipid material, shown by Mathews 

 (1897) to include both lecithin and neutral fat. The content of phos- 

 pholipids in the sperm of Echinus esculent us is about 5-5% of the 

 dry weight of spermatozoa (Rothschild and Cleland, 1952). The 

 seminal lipids of E. esculentus have been analysed more recently by 

 Cardin and Meara (1953). The material obtained by extraction of 

 1-2 1. of semen with acetone and light petroleum, consisted of 13-6% 

 neutral fat, 32-9% free fatty acids, 260% phospholipids, 9-2% 

 sterols and 18-3% of other unsaponifiable matter. The component 

 fatty acids of the non-phospholipid fraction included a low propor- 

 tion (10-1%) of saturated acids and a high proportion of unsatur- 

 ated acids with 18C (30-4%) 20C (451%) and 22C (12-3%). The 

 phospholipid fraction had a ratio of N : P=l-4 : 1, and must have 

 therefore, consisted of a mixture of monoaminophosphatides and 

 diaminophosphatides . 



Early analyses of lipids in bovine epididymal sperm were carried 

 out by Koelliker (1856) who found that over 12% of the dried 

 material is ether-extractable. About half of this content was later 

 shown by Miescher (1878) to consist of lecithin. In a study of the 

 lipid content of bull sperm, Zittle and O'Dell (1941«) have extracted 

 washed epididymal spermatozoa successively with ethanol, ether, 

 acetone and petroleum ether, and found 13% of lipid material; when 

 the procedure was repeated with spermatozoa disintegrated by sonic 



