Studies About Phospholipid Requirement Of Swimming Crab Portunus Trituberculatus

Lpids are a major energy source for crustaceans, which also play an important role in cell membrane. Dietary phospholipids(PL), particularly phosphatidylcholine(PC), have shown beneficial effects on growth, survival, the prevention of skeletal deformities and stress resistance in larvae and juveniles in several crustaceans. The studies conducted to date on the qualitative and quantitative requirements for PL in crustacean larvae and juveniles are not conclusive, depending on the criteria used to assess the optimum requirements. The objectives of this study were to evaluate the effects of PL supplementation on growth, molt, lipid metabolism and fatty acid composition of swimming crab, Portunus trituberculatus.(1) A 50-days feeding trial was conducted to investigate the effect of dietary phosphatidylcholine(PC) levels on the growth performance, molt and body composition of swimming crab, Portunus trituberculatus. Four isonitrogenous purified casein-based diets were formulated containing three PC levels, one commercial crude soya bean lecithin(SL) level. The PC-deficiency diet was designed as a control diet. Each diet was fed to triplicate groups of 15 P. trituberculatus(initially weighing, 25.42±0.10 g /crab). The occurrence of molt death syndrome(MDS) was lowest in crab fed diet with 2.0% PC. The total molting number(including success molting number and MDS) of each group was relatively higher in crab fed diets with high PC levels. Crabs fed diet with 2.0% PC obtained a significant higher weight gain(WG) and special growth rate(SGR) than PC- deficiency group(P<0.05). Crab fed diet with 2.0% PC obtained a significant higher whole body triglyceride and cholesterol levels than those fed PC-deficiency diet(P<0.05). This study showed that the 22:6n-3 and n-3/n-6 ratio of hepatopancreas and muscle increased significantly with SL addition(P<0.05). This study suggested that at least 2.0% PC should be supplemented to the casein based diet of P. trituberculatus, and dietary SL had a better effect on the muscle and hepatopancreas fatty acid profiles than the purified PC.(2) A50-days feeding trial was conducted to investigate the effect of dietary phosphatidylcholine(PC) and cholesterol levels on the growth performance, molt and body composition of swimming crab, Portunus trituberculatus. Six isonitrogenous purified casein-based diets were formulated containing three PC levels(0%, 0.5% and 1.0%) and two cholesterol levels(0.2% and 0.6%). Crabs fed different diets showed no significant difference on growth performance and molting frequency(MF)(P>0.05). Feed conversion ratio(FCR) and protein efficiency ratio(PER) were significant affected by the PC supplementation(P<0.05). The surm glouse level increased with PC and cholesterol supplementation(P<0.05). Crabs fed diets with high PC and cholesterol levels(diet 6) obtained a highest muscle lipid level, which was significantly higher than high PC and low cholesterol group(P<0.05). In this study, no significant interaction between dietary PC and cholesterol was found in relation to the growth performance of P. trituberculatus. However, a significant interaction between dietary PC and cholesterol was found in relation to the feed and protein untilization of P. trituberculatus.(3) Six experimental diets were designed with two phospholipid(PL)(0% and 1.5%) and three fish oil levels(0%, 1% and 3%) to evaluate the effects of dietary fish oil and soybean lecithin(SL) levels on growth, survival and fatty acid composition of juvenile swimming crab, Portunus trituberculatus. Diets were iso-energetic and iso-nitrogenous, and each diet was fed to triplicate groups(initially weight, 24.88±0.04 g/crab) for 59-days. Weight gain(WG) and specific growth rate(SGR) increased with dietary PL addition to 0%-fish oil supplemented diets(P < 0.05). On the other hand, WG and SGR decreased with dietary PL addition to 3%-fish oil diets(P < 0.05). Crabs fed PL supplemented diets had higher hemolymph low-density lipoprotein cholesterol concentrations and muscle crude lipid levels(P<0.05) than crabs fed a none-PL supplemented diet. The percentage of highly unsaturated fatty acids(HUFA)(% total FA) in both polar and neutral lipids fractions of muscle tissue only increased in case of PL addition to 0% and 1%-fish oil supplemented diets(P < 0.05). HUFA levels in the neutral lipids fraction of the hepatopancreas increased by dietary PL addition at each dietary fish oil level(P<0.05). In this study, both dietary fish oil and PL addition contributed to a high n-3/n-6 ratio in muscle and hepatopancreas of P. trituberculatus. In conclusion, PL addition is only meaningful with fish oil deficient diets, in which case it enhanced lipid transport and HUFA absorption efficiency, hence improving the nutritional value of the diet.