Lipid composition and oxidation status in brain of wild-caught size-class distributed Parapenaeus longirostris (Lucas, 1846)

Abstract

The objectives of the study were to characterize the lipid composition, the oxidation status (represented by the levels of malondialdehyde (MDA)), vitamin E content and the fluorescence intensity of lipid-soluble fluorescent products (LSFP) in neural tissues from males and females of wild-caught size-class distributed of the pink shrimp Parapenaeus longirostris (Lucas, 1846), trawled in the south Atlantic coast of Spain. Moreover, the mechanisms that might produce the deposition of age-pigments in relation to the physiological age of this species in its natural environment were also investigated. Three different size classes were defined for each sex, resulting in lower sizes for males than for females. The proportion of polar lipids predominated over that of neutral lipids and no significant differences were observed either between different size-classes within sex or between different sex but belonging to the same size-class. The major polar lipid classes were phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) and no significant differences were observed between different groups. However, the cerebrosides fraction showed a significant upward trend from class I to III in both males and females. The fatty acid composition of total lipids, PC, PE and PS in the pink shrimp showed, in most cases, an increase in monounsaturated fatty acids (particularly 18:1(n-9) and 24:1(n-9)) and a decrease in polyunsaturated fatty acids (primarily 22:6(n-3)) with increasing size-age. In males, the concentration of MDA (nmol g −1 brain) and fluorescence intensity (% mg −1 TL) were positively correlated ( r=0.77; P<0.02) but both were negatively correlated to carapace length in the different sizes ( r=−0.88; P<0.002 and r=−0.81; P<0.01, respectively). The concentration of vitamin E (ng mg −1 brain) was positively correlated to carapace length ( r=0.85; P<0.005) showing a parallel increase of brain membrane lipids and the most potent biological antioxidant vitamin. In females, the concentration of MDA (nmol g −1 brain), fluorescence intensity (% mg −1 TL) and vitamin E (ng mg −1 brain) were not correlated to carapace length of the different sizes (under study) and showed no significant differences between the three different size classes.The fluorescence analysis of brain LSFP was not a useful tool to separate the population into different size classes.