| Immunopolysaccharide (IPS), a product extracted from sea algae, with the characteristics similar to those of microbial polysaccharides, was used as a food additive to test its effectiveness of antidisease. Around 100 juvenile Penaeus vannamei with a body length of 3–4 cm were collected from the Shrimp Hatchery of Weihai Aquaculture Company on June 2, 1995, and were then nursed in 4 PVC tanks (100 cm×150 cm×100 cm) in the Aquarium of the Institute of Oceanology, The Chinese Academy of Sciences. Water temperature was kept at 22 - 28°C, salinity 32. The water was aerated, and changed twice a day (1/3 - 1/2 volume of water was renewed each time). No IPS was added in the food during nursery periods.
After nursery, P. vannamei with a body length of 6 - 7 cm were shifted to two PVC tanks of the same size (diameter 90 cm, height 100 cm, one for control, the other for test group, stocking density 18 pieces/tank) on August 18, 1995, when experiments of superoxide dismutase (SOD) activity, bacteriolytic (UL) and antibacterial (Ua) activities began. The controlled group was fed with food without IPS, while the test group was fed with IPS. The maintenance of shrimps was the same as the nursery period.
Experiment of phenoloxidase (PO) test was designed as the same as those of SOD, UL and Ua, test except that, for the stocking density of l6 pieces/tank, only two consecutive samples were taken because of insufficient number of shrimps. Shrimp samples with a body length of 6-8 cm were collected from October 1, 1995.
Blood samples were collected from the hearts of 4 - 5 shrimps to measure PO activities for P. vannamei. Two consecutive blood samples (each sample consisted of controlled and test groups) were collected in an 20 day's interval and the blood serum was prepared at 4°C to measure their PO activities using a Spectrometer-751. Muscle samples were taken from 2 - 5 shrimps in 10 day's intervals to measure SOD activity, UL activity to Mcrococcus lysoleikticus and Ua, activity to Escherichia coli of P. vannamei. Three consecutive muscle samples (each consisted of controlled and test groups) were collected and the supernatant of muscle homogenate was prepared by centrifugation at 4C to measure their PO, UL and Ua, activities using the Spectrometer-751.
The results show that PO, SOD, UL and most Ua activities of P. vannamei of the test groups are generally higher than those of the controlled groups, indicating the effectiveness of IPS in enhancing PO, UL, Ua, and SOD activities of P. vannamei, leading to an increase in the immunological and anti-oxidation activities (Tab.1 and Tab. 2). Further studies are needed to identify the mechanism of IPS in antidisease effect and the relationships among SOD, PO, UL and Ua activities. |
