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In order to understand the importance of particle size and agglomeration for nano-eco-toxicological studies in aquatic environments, the acute toxicity of two different types (suspended powder and colloidal) of silver nanoparticles (AgNPs) were studied in alevin and juvenilerainbow trout. Fish were exposed to each type of AgNPs at nominal concentrations of 0.032, 0.1, 0.32, 1, 3.2, 10, 32, and 100 mg/L. Lethal concentrations (LC) were calculated using a Probit analysis. Some physical and chemical characteristics of silver nanoparticles were determined. In the case of colloidal form, particles were well dispersed in the water column and retained their size; but in the case of suspended powder, particles were agglomerated to large clumps and precipitated on the bottom. In alevins, the calculated 96 h LC50 values were 0.25 and 28.25mg/L for colloidal and suspended powder AgNPs respectively. In the case of juveniles, the 96h LC50 of colloidal form was 2.16mg/L, but suspended powder did not caused mortality in fish even after 21 days. The results showed that both in alevin and juvenile stages, colloidal form is much toxic than suspended powder; this shows increase of nanoparticles size due to agglomeration, will reduce the toxicity. Silver nanoparticles are toxic materials and their release into the water environment should be avoided.

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The toxicity of imidacloprid and pirimicarb for all stages of the melon aphid, Aphis gossypii Glover, were investigated under laboratory conditions (25 ± 1 ^oC, 65 ± 5% R.H. and a photoperiod of 16:8 (L: D) h.) using a leaf dipping method. These pesticides were very toxic for first instar nymphs of A. gossypii with LC₅₀ values of 17 and 220.2 ppm for imidacloprid and pirimicarb, respectively. For other nymphal instars, values of 23.9 to 70.5 ppm and 308.8 to 781.7 ppm were recorded for imidacloprid and pirimicarb respectively. Their LC₅₀ values for adults were 90.1 and 983.1 ppm, respectively. Toxicity decreased with increasing age. Imidacloprid was more toxic than pirimicarb for all stages of development. The effect of applying sublethal concentrations of imidacloprid and pirimicarb was evaluated, also, using demographic toxicology. Longevity and population growth parameters, including intrinsic rate of increase (r_m), net reproductive rate (R₀), generation time (T_c) and finite rate of population increase (λ), were affected negatively by both insecticides. The r_m values for control, imidacloprid and pirimicarb exposed populations were 0.438, 0.150 and 0.335 female offspring per female per day, respectively. The doubling time (DT) also, was affected by imidacloprid. Overall, these results suggest that imidacloprid and pirimicarb can be effective against A. gossypii.  

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The effect of cadmium on hematological and biochemical indices of silver carp (Hypophthalmichthys molitrix) exposed to subacute (0.65ppm) and acute (3.25ppm) concentrations for 96-h test period was assessed. The results showed that Hb, Hct, RBC and MCV significantly decreased in low concentration of cadmium (p<0/05), while MCH, MCHC, WBC, glucose and cortisol were significantly (p<0/05) higher than control group in both low and high concentrations. This study reveals that some hematological and biochemical indices of silver carp, such as cortisol, can be used as suitable biomarkers in tracing Cd²⁺ contamination within water bodies.

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Silver nanoparticles (AgNPs) are widely used in consumer products mainly due to their antimicrobial action. The rapid increase in the use of nanoparticles has driven more attention to their possible ecotoxicological effects. In this study: first, acute effects of colloidal AgNPs during embryonic stage of Persian sturgeon and Starry sturgeon were investigated and then in Starry sturgeon, their short-term effects during early life stages (before active feeding commences) were analyzed. Based on the obtained results from the acute toxicity tests, AgNPs induced a dose-dependent toxicity in both species during early life stages. The short-term toxicity test was performed using 0, 0.025, 0.05 and 0.1 mg/l of colloidal AgNPs. Silver accumulation in larvae exposed to 0.1 mg/l AgNPs was recorded significantly higher than the control treatment (P<0.05). However, the obtained survival rate data did not indicate any significant differences among treatments.

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Malathion and diazinon are widely used organophosphate pesticides in the agriculture fields, especially in the north provinces of Iran. In the current study, lethal concentrations of diazinon and malathion were determined based on big head carp calculated death rates at 24, 48, 72 and 96 hours using probit analysis. Then, in a separate experiment and according to the obtained LC₅₀, the effects of these toxins on fish hematological parameters was evaluated in which fish were disturbed in 10 treatments with 3 replicates (4 different doses of diazinon, 4 different doses of malathion and 1 control for each toxin) for 7 days. Fish were exposed to different sub-lethal concentrations of each toxin (12.5, 25, 37.5 and 75% of lethal concentration (LC50 96h). After 7 days, blood samples were collected and hematological parameters including hematocrit, hemoglobin, red blood cells count, the total number of white blood cells and white blood cell differential count (the percentage of lymphocytes, monocytes, neutrophils and eosinophils) were examined. The results of acute toxicity test showed that diazinon is more toxic to big head carp compared to malathion. Also, hematological studies of big head carp exposed to diazinon showed a significant reduction in red blood cells and white blood cells with increasing toxin concentration. Meanwhile, the percentage of neutrophils remarkably increased while lymphocytes significantly decreased along with increasing the concentration of diazinon.

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Due to widespread use of nanoparticles in various fields and the possibility of entering these nanoparticles into aquatic ecosystems, it is necessary to study the effects of these nanoparticles on surrounding environment. Artemia salina nauplii as a suitable biological model in ecotoxicology were exposed to different concentrations of 0.0001, 0.001, 0.005, 0.01 and 0.1 ppm mercury ions separately and simultaneously with a constant concentration of 0.1 ppm and 1 ppm titanium dioxide nanoparticles. The mortality rate of Artemia after 48 hours and the effects of these contaminants on fatty acid profile of Artemia were investigated. Artemia mortality in co-exposure treatment showed a dual effect. The mortality in the simultaneous exposure with constant concentration of 0.1ppm titanium dioxide increased compared with separate treatment of mercury. The mortality in simultaneous treatment with constant concentration of 1ppm titanium dioxide decreased compared with the separate treatment of mercury and the effect of mercury toxicity was reduced. Also, a decrease in saturated fatty acids was observed in the simultaneous exposure of mercury and titanium dioxide nanoparticles with a constant concentration of 1ppm compared with the separate treatment of mercury. The amount of monounsaturated and polyunsaturated fatty acids in the simultaneous exposure with constant concentration of 1ppm titanium dioxide was equal to control and increased compared with separate treatment of mercury. Present findings indicate the necessity of paying more attention to the potential interactions of pollutants in aquatic ecosystems and the effects of these interactions on the bioavailability and toxicity of pollutants regarding their concentration.

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The cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae), is an important pest of canola that can considerably limit crop production through direct or indirect damage. In this study, the effects of Azadirachtin, Tondexir, Palizin, and Thiamethoxam, common insecticides used in managing the cabbage aphid, were investigated on the population growth parameters of this pest. Based on the results, the LC₅₀ values for Thiamethoxam, Palizin, Azadirachtin, and Tondexir were 0.19, 0.63, 1.00, and 3.82 g/L, respectively. Moreover, LC₃₀ concentrations of Thiamethoxam, Palizin, Azadirachtin, and Tondexir were 0.11, 0.10, 0.41, and 1.68 g/L, respectively, applied in the sublethal studies. The cabbage aphids reared on the plants treated with these insecticides had lower longevity, fecundity, and reproductive period than the control treatment. The intrinsic rate of increase (r_m), finite rate of increase (λ), net reproductive rate (R₀), and generation time (T) were lower on Thiamethoxam treatment. Tondexir and Palizin treatments had lower values than Azadirachtin. However, there was no significant difference between the Tondexir and Palizin treatments. The population treated by Azadirachtin had the highest values of growth parameters. According to the results and available information in the context of risk assessment of the studied insecticides, this research recommends the application of Thiamethoxam in the integrated pest management of cabbage aphid.

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Recently, some natural products have been used in the fields as alternative to synthetic compounds, to minimize the negative impacts to the environment. This study aimed to verify the effects of Neem-based bio-pesticide in causing acute toxicity for a fish and chronic toxicity for a microcrustacean. To this end, Danio rerio and Daphnia magna were exposed to various concentrations of a Neem-based oil formulation. In the first experiment, adults of D. rerio were exposed for 96 hours to different concentrations to determine the median lethal concentration (LC_50-96h). For D. magna, first an acute toxicity test was performed to determine the median effective concentration (EC_50-48h). Based on the EC₅₀ established in the acute test, the concentrations for the 21-day chronic toxicity test were determined. Endpoints evaluated were reproduction (number of neonates produced) and size of D. magna.The median lethal concentration for the fish was 0.22 mL L^-1, and the median effective concentration (EC_{50 - 48h}) for D. magna was 0.17 mL L^-1. In the chronic test, all concentrations affected reproduction and size of D. magna. The formulation tested may be hazardous to aquatic organisms.