The sublethal effects of (2,4-Dichlorophenoxy) acetic acid (2,4-D) on narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823).

2,4-D is a widely used phenoxy herbicide, potentially toxic to humans and biota. The objective of the present study was to reveal short term sublethal effects of 2,4-D on narrow-clawed freshwater crayfish (Astacus leptodactylus Eschscholtz, 1823), based on histology, total haemocyte counts, selected haemolymph parameters, and oxidative stress parameters. In the laboratory conditions crayfish specimens were exposed to 9 mg L-1 of 2,4-D for one week. Experiments were conducted under semi-static conditions in 20 L-capacity aquaria where 10 freshwater crayfish were stocked per aquarium. Exposure (experimental) and control groups were used and the experiments were repeated two times. No mortality and behavioural changes were recorded during the experiments. Total haemocyte counts decreased significantly, while haemolymph glucose levels increased (P<0.05), when compared to the control group. Haemolymph levels of calcium, chloride, sodium, potassium, magnesium, total protein, and lactate did not change. Exposure resulted with increased levels of malondialdehyde (MDA) only in hepatopancreas. However, results of gill FOX assay showed a significant decrease in oxidative stress parameters (P<0.05). MDA levels of gill and abdominal muscle tissues and FOX levels of hepatopancreas and abdominal muscle tissues did not change when compared to the control group. Significant histopathological alterations were observed both in hepatopancreas (multifocal deformations in tubule lumen) and gill tissue (melanisation of gill lamella). Exposure of crayfish even to a sublethal concentration of 2,4-D alters histopathology and lipid peroxidation due to stress. Biomarkers studied here seem to be useful for the assessment of adverse/toxic effects of pesticides on non-target, indicator aquatic organisms.

Sublethal propoxur toxicity to juvenile common carp (Cyprinus carpio L., 1758): biochemical, hematological, histopathological, and genotoxicity effects.

The sublethal toxicological and genotoxic potential of propoxur, a widely used carbamate insecticide against household pests, in veterinary medicine, and in public health, was evaluated on carp as a model species (Cyprinus carpio L., 1758) using the erythrocyte micronucleus test. Based on the 96-h lethal concentration, 50% (LC50) data from the U.S. Environmental Protection Agency ECOTOX Database (10 mg/L), a sublethal exposure concentration of 5 mg/L was used under static bioassay laboratory conditions. Histopathological evaluation showed no significant changes in spleen, intestine, muscle, or skin tissues. However, the following conditions were recorded: hyperemia, branchitis in primary lamella, and telangiectasis, hyperplasia, fusion, epithelial lifting, and epithelial desquamation in secondary lamella of gill tissues; hemorrhage, destruction, prenephritis, and inflammation and desquamation in the tubules; edema in the kidney; passive hyperemia, albumin, and hydropic degeneration in the liver; and hyperemia, chromatolysis, and glial proliferation in brain tissues. No statistically significant increases in micronuclei frequencies were found. Hematological parameters showed decreased hematocrit values and mean corpuscular volume values, as well as increased erythrocyte and leukocyte counts compared with the control group (p < 0.01). Plasma glucose, cholesterol, triglycerides, phosphorus, sodium, total plasma protein, chloride, and aspartate aminotransferase levels were increased (p < 0.01). Only plasma calcium and potassium levels decreased in the experimental group. Propoxur has an ecotoxicological potential on fish, a nontarget organism.

Acute toxicity, behavioral changes, and histopathological effects of deltamethrin on tissues (gills, liver, brain, spleen, kidney, muscle, skin) of Nile tilapia (Oreochromis niloticus L.) fingerlings.

Deltamethrin, a synthetic pyrethroid contaminating aquatic ecosystems as a potential toxic pollutant, was investigated in the present study for acute toxicity. The purpose of this study was to evaluate LC(50) values of deltamethrin on Nile tilapia (Oreochromis niloticus L.) fingerlings and investigate histopathological responses of fish exposed to deltamethrin. The 48 h LC(50) value for Nile tilapia fingerlings was estimated as 4.85 microg/L using static test system. In addition, behavioral changes at each deltamethrin concentration were observed closely. All fish, exposed to 5 microg/L deltamethrin revealed severe morphological alterations in the gills and liver. In the gills hyperemia, fusion of secondary lamellae and telangiectasis were observed; whereas hydropic degenerations in liver were observed in all examined fish. The results are significant for reporting acute deltamethrin toxicity in terms of behavioral and histopathological changes: Deltamethrin is highly toxic to fingerlings.

Nitrite toxicity to crayfish, Astacus leptodactylus, the effects of sublethal nitrite exposure on hemolymph nitrite, total hemocyte counts, and hemolymph glucose.

The 48-h acute toxicity range of nitrite to narrow-clawed crayfish, Astacus leptodactylus was within 22 and 70 mg L(-1) (mean 29.43 mg L(-1)). Environmental chloride (100 mg L(-1) chloride) increased the 48-h toxicity of nitrite to a range of 31 and 80 mg L(-1) (mean 49.20 mg L(-1)). Hemolymph nitrite, total hemocyte counts (THCs), and hemolymph glucose were examined in A. leptodactylus exposed to different sublethal nitrite concentrations. The same parameters were also determined for A. leptodactylus exposed to different sublethal nitrite concentrations with additional environmental chloride. Additionally, hemolymph nitrite and THCs were analyzed for crayfish exposed to nitrite-free water after 24 h following a 48-h exposure to nitrite. In the nitrite-exposed tests, hemolymph nitrite increased directly with water nitrite; however, after recovery, nitrite in hemolymph decreased. In the nitrite plus chloride-exposed tests, the accumulation of nitrite in hemolymph was relatively low compared to the nitrite-exposed tests. Thus, hemolymph to environment ratios of nitrite in the nitrite-exposed tests were higher than those of nitrite plus chloride-exposed tests. THCs decreased following nitrite exposure and, in general, increased after recovery. In the nitrite with chloride exposed and recovery from nitrite tests, THCs increased. Hemolymph glucose levels elevated following nitrite exposure, independent of water nitrite concentrations. However, with environmental chloride nitrite exposure did not cause elevation of hemolymph glucose. Hemolymph nitrite accumulation was found to be closely related to the decrease in THCs and increase in hemolymph glucose.