Composition of lipid foams from swim bladders of two deep ocean fish species

Lipid-containing deposits within the swim bladders of Coryphaenoides acrolepis and Antimora rostrata were investigated. Lipid analysis of this material, which was quite uniform from the two species, yielded the following data: neutral lipids, 36.0-41.7%; phospholipids, 53.6-56.7%; and glycolipids, 4.3-8.9%. Cholesterol (mainly in the free form) constituted 60.4%-77.8% of the neutral lipids. Sphingomyelin and phosphatidylcholine were the principal phospholipids, with sphingomyelin highest in the material from C. acrolepis and phosphatidylcholine predominant in that from A. rostrata. The overall pattern of lipids shows a resemblance to that of plasma membrane, particularly in the relatively high levels of free cholesterol, sphingomyelin, and phosphatidylserine. The lipid-to-protein ratio of the material is approximately 1.5-2 to 1. The lipids of the fine inner lining (tunica interna) of the swim bladder from a shallow water fish, the kelp bass (Paralabrax clathratus), had essentially the same composition as the much more abundant swim bladder material from the deep ocean fishes.