Seasonal and nutritional effects on the fatty acids of three species of shrimp, Penaeus setiferus, P. aztecus and P. duorarum

Abstract

The fatty acids of three species of shrimp from the Gulf of Mexico, white ( Penaeus setiferus), brown ( P. aztecus), and pink ( P. duorarum), were analyzed periodically for 1 year. The fatty acid patterns of varied species of shrimp collected at the same time of the year differed very little from each other. On the other hand, a slight but distinctive seasonal variation of the fatty acid composition, irrespective of Penaeus species, was observed. Saturated fatty acids increased during the warm seasons and decreased during the cold months, while the opposite behavior was exhibited by monoenoic and polyenoic fatty acids. When the variations in fatty acid levels were compared to the temperature of the water, there was a 2-month lag period between a change in water temperature and the corresponding variation in fatty acid composition. This slow alteration of the shrimp fatty acids suggests that the changes are effected through the food chain rather than by endogenous adjustment to an alteration in water temperature. Further studies were performed in which the fatty acid patterns of pond- and laboratory-reared shrimp were compared with those of their food. Evidence was obtained confirming the significant effect of diet on the fatty acids of shrimp lipids. Shrimp incorporated certain dietary fatty acids readily but showed little ability for the conversion of C 18 polyunsaturated fatty acids into C 20 and C 22 fatty acids of higher unsaturation. Thus, the C 20 and C 22 fatty acids which are essential for shrimp growth cannot be substituted in the diet by C 18 precursors. Considered in toto, these experiments suggest that diet exerts a strong influence on the composition of shrimp body lipids and that, contrarily, endogenous synthesis or modification occurs to a low degree.