EFFECTS OF DIETARY PHOSPHOLIPID AND CHOLESTEROL ON THE TEMPERATURE RESISTANCE OF GOLDFISH

Abstract

The temperature resistance of goldfish is increased by additions of cholesterol or phospholipid to basic diets of pablum or pablum and pilchard oil. The relative effectiveness of these treatments varies with the season and with the duration of the feeding experiment. In low-temperature resistance tests, the cholesterol effect was most marked during the earlier period of chilling and the suggestion is that cholesterol increases the capacity of fish to resist cold narcosis—not death. In heat, resistance tests, the phospholipid-fed fish showed a tendency toward heat narcosis which was not evident with cholesterol-fed animals. Increased temperature resistance was closely correlated with increased tissue cholesterol but only weakly correlated with the less modified tissue phospholipid. Although these diets also produced definite changes in total lipid content, moisture content, unsaturation of total lipids, and the cholesterol/phospholipid ratio, no evident correlation between these factors and temperature resistance of the goldfish was found. Data are discussed in relation to several theories of temperature death.