Toxic Effects Of Microcystis Aeruginosa On The Ingestion, Digest, And The Activities Of Serum And Digestive Enzymes Of Silver Carp

Cyanobacterial blooms occur frequently in fresh water due to the excessivegrowth and production of Microcystis and some cyanobacteria can producecyanotoxins, which are harmful to the aquatic environment and organisms.Microcystins (MCs) are hepatotoxin produced mainly by Microcystis aeruginosa andthey are highly toxic to the liver and kidney of fish. The aim of the present study wasto determine the ingesting rate and digesting rate of silver carp to toxic or nontoxicMicrocystis aeruginosa, to detect the activities of serum enzymes such as AST, ALTand ALP and digestive enzymes (tripsin and amylase), and to evaluate the liverhistopathology of silver carp exposed to toxic or nontoxic Microcystis aeruginosa byingesting or gavage. The main results obtained in this study are shown as thefollowing:（1）The ingesting rate and digesting rate of silver carp to toxic Microcystisaeruginosa were191.37±8.46cells/g·h and31.92±3.54％, respectively, while tonontoxic Microcystis aeruginosa, they were220.77±12.13cells/g·h and28.64±14.65％. This result suggests that silver carp can ingest Microcystis aeruginosa but withrelatively lower digestive rate.（2）The activities of serum enzymes AST, ALT and ALP were totally promotedin the fish after they ingested toxic or non-toxic Microcystis aeruginosa for acomparatively longer time, indicating that Microcystis probably disturbs the hepatofunction of silver carp.（3）In the acute gavage test, we found that the activities of serum enzymes werealso totally increased in the fish after they were exposed to toxic or non-toxicMicrocystis aeruginosa by gavage.（4）Trypsin activity in the gut of silver carp increased when the fish was fedwith toxic Microcystis aeruginosa while it decreased in the fish hepatopancreas ofsilver carp. However, the activity of amylase in both gut and hepatopancreas of silver carp increased when the fish ingested toxic or nontoxic Microcystis aeruginosa.（5）We also found that Microcystis-exposure resulted in obvious injure in fishhepatopancreas, for example, cellular swelling and intracytoplasmic vacuolizationwithin the liver and apoptotic cell increased in fish hepatopancreas when the fish wereexposed to either toxic or nontoxic Microcystis.(6) The results of this study indicate that Microcystis-exposure not only affectsfish ingesting rate and digesting rate and the activities of serum enzymes anddigestive enzymes, but also causes damage to fish hepatopancreas, indicating thatMicrocystis-exposure is toxic to silver carp.