Effects Of Oscillatoria Sp. On Growth And Immune Activities Of Litopenaeus Vannamei

Oscillatoria sp. is a kind of blue-green microalgae flourished in prawn ponds. Some species of Oscillatoria sp. could produce toxins, which could endanger breeding animals. In the research, Litopenaeus vannamei was exposed to the nutrient solution of Oscillatoria sp. and its components. In the next parts, different concentrations of Oscillatoria sp. and its crushing liquid were added into the culture water of L. vannamei. The survival rate, length, weight, activity of SOD、POD、PO、ALP、GST and anti-bacteria activity of prawn were measured. The main research results are as follows:1. With the rise of temperature, the survival rate of L. vannamei in the suspension and components of Oscillatoria sp. in logarithmicphase would reduce. When temperature was32℃, the survival rate of L. vannamei in microalgae suspension was the lowest, followed by which of prawn in algae cell contents, finally in algae cell fragments and cell-free medium. The survival rate of prawn in algae suspension and algae cell contents was20%and30%, respectively. At different temperature, the survival rate of prawn in algae suspension and algae cell contents was both lower than which of prawn in algae cell fragments or cell-free medium. So algae suspension and algae cell contents were the main components to effect prawn when aglae was in logarithmicphase at different temperature.2. When salinity was16,24or32, the effect of the suspension and components of Oscillatoria sp. in logarithmicphase on prawn was different from one another. The survival rate of prawn in algae suspension and algae cell contents was both lower than which of prawn in algae cell fragments or cell-free medium. So algae suspension and algae cell contents were the main components to effect prawn when aglae was in logarithmicphase at different temperature. When salinity was24, the survival rate of prawn in algae suspension, algae cell contents, algae cell fragments, cell-free medium and control group was40%,50%,60%,80%and90%, respectively. It showed that at breeding temperature and salinity, prawn could be influenced by the cell-free medium in a certain degree, while the effect of the cell fragments on prawn could be not big.3. The survival rate of prawn in the suspension and components of Oscillatoria sp. in decline phase would reduce with the rise of temperature. When temperature was20℃,26℃or32℃, the effect of algae cell contents and algae suspension on prawn was bigger than other components. Prawns in algae cell contents died completely, and the survival rate of prawn in algae suspension was10%when32℃. It showed that at different temperature, algae suspension and algae cell contents were the main components to effect prawn when aglae was in decline phase.4. When salinity was16,24and32, the survival rate of prawn in cell-free medium of Oscillatoria sp. in decline phase remained unchanged, while which of prawn in algae suspension and the other components appeared a trend that first increased and then decreased. The effect of algae suspension and algae cell contents on prawn was bigger than other components, when different salinity. When salinity was24, the survival rate of prawn in algae suspension and algae cell contents reached their maximums,30%and40%, respectively. And the maximums were lower than which in logarithmicphase. It showed that the survival rate of prawn in algae suspension and algae cell contents of Oscillatoria sp. in decline phase was more remarkable than which in logarithmicphase. So algae suspension and algae cell contents were the main components to effect the survival rate of prawn at different temperature and salinity, whether aglae was in logarithmicphase or decline phase.5. With the increasing of concentration of Oscillatoria sp., the survival rate, body length and weight of prawn declined (P<0.05). When the concentration of Oscillatoria sp. in water was22.5mg/L, the survival rate, body length and weight of prawn decreased by59.00%,54.05%and91.60%. Low concentration of Oscillatoria sp. could increase enzyme activity; while high levels of Oscillatoria sp. could inhibit enzyme activity and growth of prawn. When the concentration of algae was2.5mg/L, GST reached its maximum(39.05U/mL). When the concentration of algae was12.5mg/L, SOD, PO, ALP and anti-bacterial activity reached their peaks, the maximums were71.74U/mg,15.40U,73.62U/g and0.38U/mL, respectively. When the concentration of algae was17.5mg/L, POD reached its maximum(0.46U/mg).6. The survival rate, body length and weight of prawn could be significantly (P<0.05) affected by the crushing liquid of Oscillatoria sp.. With the increasing of concentration of Oscillatoria sp., the survival rate, body length and weight of prawn declined (P<0.05). When the concentration of Oscillatoria sp. in water was22.5mg/L, the survival rate, body length and weight of prawn decreased by58.21%,53.13%and88.97%. Low concentration of Oscillatoria sp. could increase enzyme activity; while high levels of Oscillatoria sp. could inhibit enzyme activity and growth of prawn. And SOD、POD、PO、 ALP、GST and anti-bacterial activity of prawn were also significantly (P<0.05) affected. When the concentration of algae was2.5mg/L, GST reached its maximum(40.91U/mL). When the concentration of algae was7.5mg/L, POD、SOD、ALP and anti-bacterial activity reached their peaks, the maximums were0.39U/mg,75.31U/mg,88.86U/g and0.48U/mL, respectively. When the concentration of algae was12.5mg/L, PO reached its maximum(14.13U). The peaks of enzymes moved forward than fresh algae liquidliquid. The results above showed that the harmful metabolite produced by the crushing liquid was more than which produced by fretsh algae liquid.