Effects of light color change on carbohydrate-related enzymes in Litopenaeus vannamei

The purpose of this study was to investigate variations of glucose content, lactic acid and carbohydrate-related enzymes in Litopenaeus vannamei subjected to one changing color light treatment (blue to green, BG) and two constant color light treatments (green, G; blue, B). Sampling five inter-molt stage shrimps to assay the hemolymph glucose, the hexokinase (HK, EC 2.7.1.1) and pyruvate kinase (PK, EC 2.7.1.40) activities of hepatopancreas at 7 a.m., 9 a.m., 1 p.m., 2 p.m., 4 p.m. and 8 p.m. on the following days: day 1, 3, 5, 10, 20 and 40 of the experiment. The hemolymph glucose content had a small increase after the light on, but the hemolymph lactic acid content did not. The HK activities of shrimps in B light treatment and G light treatment decreased after switching on the light, but those in BG light treatment increased. And the PK activities in all treatments did not have a significant change. A significant effect of rhythmic fluctuating light color on glucose, lactic acid, HK and PK activities was found in the beginning of the experiment, but this effect disappears gradually when the experiment went on. Compared with BG and G light treatment, the fluctuations of HK and PK activities of shrimps in B light treatment were more acute and it took longer time to be stable. From results, we knew that the anaerobic metabolism of shrimps under light color change condition was high and continued for a long time at the beginning of experiment, the carbohydrate utilization was high when shrimps get acclimatized to the light condition, and the high carbohydrate utilization might be beneficial to growth of shrimps.