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UBC Theses and Dissertations

Temperature tolerance of goldfish (Carassius auratus) in relation to the degree of unsaturation of body lipids, the cholesterol, phospholipid, fatty acid, and water content of the tissues. Cottle, Merva Kathryn


Ten different fats (three in duplicate) including natural and hydrogenated fats were arranged in four series of diets to allow a range in degree of saturation of diet in each series. These were fed to 1300 goldfish (100 fish per fat diet). The degree of unsaturation of fish lipid altered in accordance with the degree of unsaturation of the diet and the tolerance of the fish to high and low temperatures was modified. In none of the four series was there a precise correlation between melting point of total lipids and degree of tolerance to high and low temperatures. Since total lipid is not necessarily protoplasmic lipid it is possible that the degree of unsaturation of protoplasmic lipids (phosphatides) and temperature tolerance of the fish would show a more precise correlation. Changes occuring in water content, lipid content, and lipid constituents of fish tissues and iodine values of total lipid were studied in goldfish acclimatized to 5°, 15°,20°, and 35° C. Water content increased while lipid content decreased with a rise in the temperature of acclimatization of fish. The cholesterol : phospholipid ratio varied inversely and the cholesterol : fatty acid ratio varied directly as both the water content and temperature of acclimatization. Iodine values of the total fish lipid increased with a decrease in temperature of acclimatization. It is concluded that in the process of acclimatization to different temperatures, changes in the degree of unsaturation of total lipid as well as possible changes in permeability to water occur and that both factors may be of importance in resistance of the fish to further thermal changes.

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