| As a new type of antiparasitic drugs, Ivermectin(IVM) has been used to prevent and control nematodes and arthropod parasites in vivo and in vitro. It has been widely applied in stock raising and aquaculture because of its broad spectrum and high efficiency. It also has been regarded as one of the best antiparasitic drugs at the present time. In this study, the acute toxicity and tissue damage of IVM to carp(Cyprinus carpio), the reproductive toxicity of IVM to male crucian carp(Carassius auratus) and the distribution of IVM in simulated micro-cosmos system was tested, respectively. In order to understand the toxicity of IVM to cyprinidae fish and its behavior in the environment after treatment.To evaluate the acute toxicity and tissue damage of IVM on songpu mirror carp, IVM was given by oral administration at the dosage of 1.30, 1.69, 2.19, 2.86, 3.71, 4.83, 6.27, 8.16 mg/kg respectively. Blank control and solvent control were set meanwhile. The experimental fish were continuously observed for 96 h after IVM treatment. The results showed that the LD50 of IVM to songpu mirror carp at 96 h was 4.04 mg/kg with 95% confidence of 3.42~4.80 mg/kg. Compared with control groups, no significant difference was found in the number of red blood cells(RBCs). However, the number of white blood cells(WBCs) reached a peak at the dose of 2.86 mg/kg and then decreased with the increase of dosage. The hemoglobin(HGB) exhibited a dose-dependent rise from the dosage of 2.86 mg/kg. After oral administration of IVM at the dose of 4.83 mg/kg, tissues’ obvious pathological changes of songpu mirror carp began to be observed. The intestinal villis became necroticed and shed in intestinal cavity, liver cells were atrophied and hepatic sinusoid turned larger, tubular epithelial cells started degenerating and necrosing, and myocardial fibers began to atrophy and degenerate. The above results suggested that IVM will not damage the tissues of carps at the normal dose of 0.3 mg/kg, but will cause gradually poisoning with the increase of the dosage.In order to evaluate the IVM’s reproductive toxicity on male Crucian carp, experimental fish were randomly classified into A, B, C and D groups according to the different oral dosages of IVM(0, 0.30, 0.90 and 1.50 mg/kg respectively, once a day for 3 days in a row) and the serum, testis and the brain tissues were collected after 8 days of drug treatment. The gonadosomatic index(GSI), testosterone and estradiol in serum and testis, γ-aminobutyric acid content in serum and brain tissues, ultra-structure of spermatozoa and gonadal tissue were determined. The results indicated that GSI gradually decreased with the increase of drug dosage and GSI in group C and D were significantly lower than that of the control group(p<0.05). The contents of testosterone, estradiol and γ-aminobutyric acid exhibited a trend of first increases and then decrease and reached the peak at group B. Sperm longevity gradually decreased and the motion time also decreased in II and III level sperms with the increasing dosage of IVM, which wass especially obvious in group C and D(p<0.05). The motion time increased in IV level sperms and was obvious in group B, C and D(p<0.05). No significant differences were found in ultra-structure of spermatozoa and gonadal tissues. This study showed that IVM had no distinct reproductive toxicity to male Crucian carp at the normal therapeutic dosage but can cause the seriously potential reproductive toxicity at a high concentration.To study the IVM distribution in the pond, two sets of the same micro-cosmos systems containing ornamental carp(Cyprinus carpio haematopterus), amazon sword plant(Echinodorus amazonicus), mollusk(Cipangopaludina cahayensis), freshwater and sediment, were built up and the natural pond environment was simulated here. The water administration with IVM at a dosage of 1.6×10-4 mg/L and the oral administration with a dosage of 0.30 mg/kg were implemented respectively. After the treatment, two systems were sampled on 0.5 h, 1, 7, 15, 30, 45, 60 and 70 d, and the samples included the roots and leaves of amazon sword plants, the visceral mass and muscle of fish, the soft tissue of mudsnails, the sediment and water. The concentration of IVM in samples was measured by ELISA. The results showed that the peak concentrations of IVM in the visceral mass and muscle of fish, the roots and leaves of amazon sword plant, the soft tissue of mudsnail, the sediment and water were 259.818 and 149.268 ng/g, 192.099 and 67.080 ng/g, 35.914 and 31.323 ng/g, 38.584 and 44.824 ng/g, 24.750 and 24.987 ng/g, 0.132 and 0.115 ng/m L, 2.900 and 3.863 ng/g, respectively. Based on the study above, the accumulations of IVM in various components of water environment were different under different modes of administration. There was obvious accumulation of IVM in fish, amazon sword plants and mudsnails. The concentration of IVM in sediment was higher than that in water, and eliminated slowly.These results told us that IVM is high toxicity to carp and crucian carp, and could cause tissue damage and potential reproductive toxicity of cyprinidae fish after inappropriate use. The biological effects of IVM accumulation on fish, aquatic plant and mudsnail were obvious. And its rapid sorption to sediment particles and high persistence in aquatic sediments had also been proved. The evidences above suggested that the use of IVM should strictly follow the instruction in the process of breeding. |
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