Susceptibility of epigeic earthworm Eisenia fetida to agricultural application of six insecticides.

Ecotoxicological risks of agricultural application of six insecticides to soil organisms were evaluated by acute toxicity tests under laboratory condition following OECD guidelines using the epigeic earthworm Eisenia fetida as the test organism. The organochlorine insecticide endosulfan (LC(50) - 0.002 mg kg(-1)) and the carbamate insecticides aldicarb (LC(50) - 9.42 mg kg(-1)) and carbaryl (LC(50) - 14.81 mg kg(-1)) were found ecologically most dangerous because LC(50) values of these insecticides were lower than the respective recommended agricultural dose (RAD). Although E. fetida was found highly susceptible to the pyrethroid insecticide cypermethrin (LC(50) - 0.054 mg kg(-1)), the value was higher than its RAD. The organophosphate insecticides chlorpyrifos (LC(50) - 28.58 mg kg(-1)), and monocrotophos (LC(50) - 39.75 mg kg(-1)) were found less toxic and ecologically safe because the LC(50) values were much higher than their respective RAD.

Studies on relative toxicities of six insecticides on epigeic earthworm, Perionyx excavatus.

The 96 h LC(50) values of six insecticides were determined on a non-target epigeic earthworm Perionyx excavatus under laboratory conditions. Cypermethrin was found most toxic to P. excavatus (LC(50)-0.008 mg/kg), followed by endosulfan (LC(50)-0.03 mg/kg), carbaryl (LC(50)-6.07 mg/kg), chlorpyrifos (LC(50)-7.3 mg/kg), aldicarb (LC(50)-10.63 mg/kg) and monocrotophos (LC(50)-13.04 mg/kg). When these LC(50) values were compared with their respective recommended agricultural doses, aldicarb and carbaryl appeared more dangerous than other pesticides because of their lower LC(50) values than their respective recommended agricultural dose. Mean lethal time to cause 50% mortality at recommended agricultural dose (LT(50)) also indicated that aldicarb achieved the fastest LT(50) (26 h) followed by endosulfan (38 h) and carbaryl (44 h) indicating the danger of these pesticides to P. excavatus.

Toxicity of methanol to fish, crustacean, oligochaete worm, and aquatic ecosystem.

Static renewal bioassays were conducted in the laboratory and in outdoor artificial enclosures to evaluate toxic effects of methanol to one teleost fish and two aquatic invertebrates and to limnological variables of aquatic ecosystem. Ninety-six-hour acute toxicity tests revealed cladoceran crustacea Moina micrura as the most sensitive to methanol (LC50, 4.82 g/L), followed by freshwater teleost Oreochromis mossambicus (LC50, 15.32 g/L) and oligochaete worm Branchiura sowerbyi (LC50, 54.89 g/L). The fish, when exposed to lethal concentrations of methanol, showed difficulties in respiration and swimming. The oligochaete body wrinkled and fragmented under lethal exposure of methanol. Effects of five sublethal concentrations of methanol (0, 23.75, 47.49, 736.10, and 1527.60 mg/L) on the feeding rate of the fish and on its growth and reproduction were evaluated by separate bioassays. Ninety-six-hour bioassays in the laboratory showed significant reduction in the appetite of fish when exposed to 736.10 mg/L or higher concentrations of methanol. Chronic toxicity bioassays (90 days) in outdoor enclosures showed a reduction in growth, maturity index and fecundity of fish at 47.49 mg/L or higher concentrations of methanol. Primary productivity, phytoplankton population, and alkalinity of water were also reduced at these concentrations. Chronic exposure to 1527.60 mg/L methanol resulted in damages of the epithelium of primary and secondary gill lamellae of the fish. The results revealed 23.75 mg/L as the no-observed-effect concentration (NOEC) of methanol to freshwater aquatic ecosystem.

Acute toxicity of cadmium to fish Labeo rohita and copepod Diaptomus forbesi pre-exposed to CaO and KMnO4.

96-h LC50 values of cadmium (Cd) to fish Labeo rohita and the copepod Diaptomus forbesi, determined by static bioassays, were, respectively, 89.5 and 10.2 mg/l. LC50 values increased significantly when fish pre-exposed to 100-350 mg/l CaO or 0.5-1.5 mg/l KMnO4 for 4 d and the copepod to 20-70 mg/l CaO or 0.25-1.0 mg/l KMnO4 for same period. The LC50 values also increased when the pre-exposure period of CaO was increased to 12 d at concentration 100 mg/l for fish and 20 mg/l for copepod. All fish died when pre-exposed to 1.5 mg/l KMnO4 for 8 d. But LC50 values of Cd to copepod increased when pre-exposure period of 0.5 mg/l KMnO4 was increased from 4 to 8 d.

Effect of potassium permanganate, cobalt chloride and vitamin B complex on the haematological parameters of cadmium treated common carp, Cyprinus carpio.

Effect of potassium permanganate, cobalt chloride and vitamin B complex on the haematological parameters of common carp Cyprinus carpio were markedly influenced by a treatment of 2.5 mg/l Cd in the laboratory for 96 hours. Hb% and ESR values were increased but the RBC and PCV values were reduced. Treatment of KMnO4 (1 mg/l) or CoCl2 (2 mg/l) induced a further reduction of RBC of the Cd treated fish. But parameters like PCV, MCV and MCH of Cd treated fish were not affected by the treatment of KMnO4 and CoCl2. Intramuscular injection of vitamin B complex did not produce any impact on ESR and MCV values of the Cd treated exposed fish but most of the other parameters of such fish were found comparable to control indicating that vitamin B complex could counteract Cd to reduce its ill effect.

Effect of potassium permanganate, cobalt chloride and vitamin B complex on the haematological parameters of cadmium treated common carp, Cyprinus carpio

Effect of potassium permanganate, cobalt chloride and vitamin B complex on the haematological parameters of common carp Cyprinus carpio were markedly influenced by a treatment of 2.5 mg/l Cd in the laboratory for 96 hours. Hb

and ESR values were increased but the RBC and PCV values were reduced. Treatment of KMnO4 (1 mg/l) or CoCl2 (2 mg/l) induced a further reduction of RBC of the Cd treated fish. But parameters like PCV, MCV and MCH of Cd treated fish were not affected by the treatment of KMnO4 and CoCl2. Intramuscular injection of vitamin B complex did not produce any impact on ESR and MCV values of the Cd treated exposed fish but most of the other parameters of such fish were found comparable to control indicating that vitamin B complex could counteract Cd to reduce its ill effect.