The Toxicity Impact Of Microcystis Aeruginosa And Microcystin On Crayfish (Procambarus Clarkii)

Microcystis aeruginosa is the most familiar algae in the cyanobacterial bloom, which produces microcystin. It can cause serious harms to the aquaculture. It frequently erupts in the high temperature season in the fresh water lake or the pond. Microcystin is a monocyclic heptapeptides toxin. It can cause swelling and congestion of liver and a series of enzyme changes. Research indicates that Microcystin can damage the ultrastructure of liver cytoskeleton, even the hemorrhage and necrosis of liver. Because of the stability of MCs, it can cumulate in the food cycle. In the same time, MCs can induce apoptosis, stress reaction and even destroy DNA directly. It has been confirmed MC in drinking water have great relevance to primary liver cancer and colorectal cancer incidence. It has becomed one of the three major environmental risk factor result in liver cancer in southern China. Microcystis aeruginosa and microcystin have caused serious harm to aquatic animals and even human health.Crayfish (Procambarus clarkii), important aquatic economic animals, has become a research focus in recent years because of its living place such as: river, ditches, pond, farmland, which are the place prone to algal blooms. When cyanobacterial blooms, Microcystin may be enriched in the hepatopancreas of crayfish. It needs more research to confirm whether MCs could be passed to human by eating crayfish.Based on the above situation, This article summarized the toxicological effects induced by microcystins,including liver and kidney of microcystin toxicity,induction of apoptosis,regulation of transcription-related genes affect the expression of related proteins and the immune system and so on. This paper attempts to the immune toxicity on crayfish caused by Microcystin. The larvaes was put in different concentrations of M. aeruginosa water. Recorded the survival situation and observed the changes of juvenile. Using transmission electron microscopy (SEM) to observe hepatopancreas Changes in the ultrastructure. Set different concentrations of M. aeruginosa, the crayfish was exposed to the M. aeruginosa. The changes of THC represent the impact on the lymphocytes after the M. aeruginosa explore; by studying the several changes of oxidation related enzymes to analysis of the immune oxidative stress effect resulted by M. aeruginosa. In this paper, the author used a use a new method to identify the phagocytosis of blood-- E. coli which can express green fluorescent protein was used as phagocytosis sources. In this method, different concentrations of Microcystin effect on in vitro cultured lymphocytes of crayfish. Compared the difference phagocytic ability of lymphocytes after Microcystin explore with the normal lymphocytes. In some way the result suggest the role of Microcystins, such as cell injury and the immunity changes. Through the above techniques route, the author attempted to research the chronic toxicological mechanisms of M. aeruginosa and Microcystins. The result shows that: (1) Microcystis aeruginosa can significantly reduce the survival rate of crayfish larvae. When algae cells reached 5.0×106 cells/ml, the survival rate was only 68.33% on the 26th day, which is significantl lower than the control group(p<0.05); the 1.0×107 cells/ml group was significantly lower than the control group on the 19th day with 61.67% surviva(lp<0.05),when the experiment finished ,the survival rate was only 48%. (2) The hepatopancreas of larvae crayfish became darkered and hepatopancreas cells were observed to be damaged under the transmission electron microscopy. (3) THCs of the adult crayfish increased significantly and stayed at a high level after being exposed for 1d. There were not significant difference for hemocyanin content difference at the beginning while significant decreased at 5d(p<0.05). The activity of T-SOD in serum was inhibited after 1d, and was activated to a high level at 5d. The activity of POD and PO showed fluctuation trend. The activity of Na+/K+-ATP in gill dropped significantly after 1d (p<0.01), then increased and stayed at a higher level finally. The result indicated that Microcystis aeruginosa has negative impact on the survival of the juvenile crayfish and affect immunity of the adult crayfish which may cause loss of grow-out of crayfish. (4)The change of phagocytosis of lymphocytes after microcystin effect showed that microcystin can inhibit the phagocytic index of lymphocytes, and presence a certain dose effect of microcystin. However the percentage of phagocytic had no significant changes before or after the toxin exposure.These results suggest that Microcystis aeruginosa have a certain impact on the juvenile survival and immunity to crayfish(Procambarus clarkii):juvenile’s survival rate was reduced significantly; external morphology and ultrastructure of hepatopancreas shows a significant change; the immune enzymes activity finally tend to the the initial value or maintain in a certain bound, the changes shows that Microcystis aeruginosa existence influence on the immunity of crayfish, but the influence was in the tolerance range. The microcystin as a hepatotoxin, can affect the immunity of lymphocytes in the same time.