Chronic ingestion of saturated hydrocarbons by rainbow trout: influence of dodecylcyclohexane and pristane on lipid metabolism

Growth reduction in trout induced by naphthenic and isoprenoid hydrocarbons (Dodecylcyclohexane and pristane)

Rainbow trout were fed a diet containing 1% dodecylcyclohexane or pristane for 9 weeks. Feed intake was recorded daily and weight gain every 3 weeks. These animals were compared with fish receiving a hydrocarbon-free diet (groups fed ad libitum and pair-fed groups for which the ration provided was the amount of food consumed by the hydrocarbon-contaminated fish, the day before). The total food ingested by the pristane and dodecylcyclohexane groups amounted to 66 and 70%, respectively, of that eaten by the controls. The final mean weight of the controls was twofold their initial weight. The average weight gain of the dodecylcyclohexane and pristane groups was 37 and 25%. During the same period the fish of the pair-fed groups gained approximately 70% of their initial weight. Significant effects of hydrocarbon consumption on food conversion factors, viscerosomatic index, hepatosomatic index, and liver lipid concentration were observed. The results are discussed in relation to the possible causes of such changes.

Hydrocarbons disposition, lipid content, and fatty acid composition in trout after long-term dietary exposure to n-alkanes

Uptake, distribution, and storage of n-alkanes was studied in rainbow trout receiving a diet containing 1% normal paraffins in the C13-C22 range. After 3 months, the concentration of hydrocarbons deposited in the whole body reached a steady equilibrium value in the range 700-900 ppm. The most pronounced deposition occurred in the adipose tissue. The n-alkane pattern in the whole body exhibited a profile different from that of the alkane mixture ingested. The alkanes around C20 were not retained to any great extent, but as the chain length decreased, the relative amount stored increased. In the liver a marked predominance of even-carbon chain length was observed while in whole fish and in other organs such a phenomenon did not occur. After 5 months, total lipids in the carcass were significantly lower in the test group than in the control group. At the end of the accumulation period, a significant enhancement in the proportion of odd- and even-chain saturated fatty acids from C14:0 to C18:0 was noted in carcasses of hydrocarbon-fed fish. Myristic, pentadecanoic, and heptadecanoic acids were also significantly more abundant in the liver and adipose tissue of contaminated fish. This increase is attributed to the terminal oxidation of the predominant n-alkanes in the diet into the corresponding fatty acids. During the depuration period, one-half of the trout in each group were fed a hydrocarbon-free diet, while the others were starved. After 2 months, both starved and fed trout had lost approximately 50% of the amount of total n-alkanes stored. The n-alkanes longer than C16 were well retained, while short-chain alkane concentration decreased rapidly.