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Toxicity of the organophosphate, diazinon was studied in grass carp (Cetenopharyngodon idella) weighing 5±1.0g, under static water quality condition at 16°C. Also, some hematological and biochemical variables of fish weighing 50±5.0g were studied 12 hours post-exposing fish to the toxicant at sublethal concentration of 5.6mg/L at 16°C. Values of 18.19, 17.21, 16.68, and 15.13mg/L, were obtained as LC₅₀ after 24, 48, 72 and 96 hours post-exposing fish to the toxicant, respectively. Levels of red blood cells (RBC), hematocrit (PCV), hemoglobin (Hb), mean corpuscular hemoglobin concentration (MCHC), leukocyte count (WBC), lymphocyte and monocyte were significantly lower in the exposed fish than control fish (p<0.05), whilst values of polymorphonuclear cells (PMN) and myelocytes counts were higher in the test group (p<0.05). In addition, the levels of aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were significantly lower in fish exposed to the toxicant (p<0.05), while the level of alanine aminotransferase (ALT) was higher in experimental fish (p<0.05) than control fish. The levels of glucose and triglyceride were higher in fish exposed to toxicant than control fish. However, such differences were only significant for glucose level (p<0.05). In contrast, the levels of total protein and cholesterol decreased insignificantly in fish exposed to the toxicant compared to those in control fish (p>0.05). The obtained results show that although diazinon can be classified as a slight toxic chemical for grass carp, the toxicant negatively affects some immunophysiological functions of the fish including immunocompent cells.

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The brine shrimp, Artemia spp., is widely used in ecotoxicological research as a biological index. In the present study, aquatic stability and acute toxic effects of TiO₂, CuO and ZnO nanoparticles (NPs) on Artemia franciscana were investigated. Acute exposure was conducted in sea water with different concentrations of selected nanoparticles at 24h, 48h, 72h and 96h. The mortality rate of A. francisca increased significantly with increasing concentrations and duration of exposure of all NPs. The toxicity pattern of metal oxides to A. francisscana was as follows: CuO>TiO₂>ZnO. Our results point to the fact that both TiO₂ and ZnO NPs exhibited moderate toxicity to Artemia larvae in 24h as compared with CuO, regardless of their size and concentrations.

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The aim of this study was to investigate acute toxicity (96-hr LC₅₀ and lethal concentrations) of waterborne metal mixture (Pb+Mn) for the fish, Catla catla, Labeo rohita, Cirrhina mrigala, Ctenopharyngodon idella and Hypophthalmichthys molitrix. The extent of metals bio- accumulation in fish body organs viz. gills, liver, kidney, fins, bones, muscle and skin at both 96-hr LC₅₀ and lethal concentrations were also determined. The criteria of toxicity used during these experiments were mortality upon the 90-day old fish species. The tests were performed, separately, at constant pH (7), temperature (30°C) and hardness (200 mg L^-1) of water with three replications for each test dose. The overall sensitivity of five fish species, determined in terms of LC₅₀ and lethal concentrations, against metals mixture (Pb+Mn) varied significantly. Among five fish species, H. molitrix were significantly more sensitive to metals mixture with mean 96 hr-LC₅₀ and lethal concentrations of 69.36±0.03 and 114.51±0.02, respectively. Regarding overall responses of five fish species for their ability to accumulate metals, kidney appeared as an organ to amass significantly higher amounts of metals, followed by that of liver while it was significantly least in fish muscles. Accumulation of the metals in fish body followed the general order: kidney>liver>fins>gills >skin>bones>muscle.

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Ichthyophthirius multifiliis is one of the parasitic diseases of fish infecting both farmed and wild freshwater fishes at all ages. This parasite penetrates into the fish skin epidermis and creates white spots on the skin accordingly, the disease caused by this parasite is also called white spot disease. Formalin, chloramine-T, malachite green, and other chemical compounds may be used against this disease; however, each of these compounds leads to harm to humans and the environment in some way; hence, it seems necessary to find natural alternative compounds to treat this disease. This study aimed at determining the effectiveness of alcoholic extract of Terminalia catappa L. at different concentrations (0-850 mg/L) and exposure times (1-3 h) in vitro. The findings were statistically compared with those of the control and positive control groups (formalin at a dose of 15 ppm). The results of the present study revealed that the effectiveness of T. catappa L. alcoholic extract on the theront stage of the I. multifiliis parasite is a function of time and concentration and with increasing concentration and time, its effect will enhance. The results of this study indicated that after two hours, a dose of 850 mg/L killed 100% of the theronts and it is the most appropriate dose, even though the possibility of applying this dose to treat live fish should be investigated.