Pesticide-free Water Research Articles

Toxicity of fenvalerate to caddisfly larvae: chronic effects of 1- vs 10-h pulse-exposure with constant doses

Episodic pollution events such as runoff or spraydrift can lead to a short-term (few hours) contamination of aquatic ecosystems with pesticides. So far, different short-term exposures with respect to long-term effects have not been studied. In the present study, caddisfly larvae, typical for agricultural streams ( Limnephilus lunatus Curtis, 2nd and 3rd instar) were exposed for 1- vs 10-h to three different equivalent doses (μg h) of fenvalerate. After transfer into an artificial stream microcosm with pesticide-free water, chronic effects were observed over 240 days. Comparison of 1- and 10-h exposure revealed that 1-h contamination leads to stronger effects. The differences were significant for the sublethal endpoints emergence pattern and dry weight of adults ( ANOVA, Fisher's PLSD; P<0.05). In terms of exposure dose, the difference between 1- and 10-h exposure equals a factor of 6 as a mean of all endpoints studied. The following significant effect levels for the 1-h exposure were obtained for the different endpoints investigated: reduced emergence success and production at 0.1 μg l −1, temporal pattern of emergence at 0.001 μg l −1, dry weight of adults at 0.01 μg l −1.

Cholinesterase Activity and Hematological Parameters as Biomarkers of Sublethal Molinate Exposure in Anguilla anguilla

Cholinesterase (ChE) activity was measured in plasma, whole blood [using 5,5′-dithiobis(2-nitrobenzoic acid) and 2-PDS as chromophores], brain, and whole eyes of Anguilla anguilla exposed to a sublethal concentration of 11.15 mg/L (one-third of the 96-h LC50) of the carbamate herbicide molinate. ChE activity was evaluated after 6, 24, 48, 72, and 96 h of pesticide exposure. Results indicated that ChE activity in eel tissues decreased as time of exposure increased, especially in eel blood. Eels exposed to molinate were transferred to a pesticide-free water for a recovery period of 4 days and ChE activity was also evaluated. Results indicated that ChE activity for those animals with preexposure to the carbamate was still different from the controls even after the recovery period. The use of hematological parameters for assessing the toxicity of molinate in A. anguilla was also studied. The parameters included the measurement of blood proteins, hematocrit, hemoglobin, erythrocytes, and leukocytes. Molinate exposure produced a decrease in all the hematological parameters tested, which was significant only during the recovery period. These results indicate that ChE activity, as well as hematological parameters, may be useful as a diagnostic test for molinate exposure in aquatic organisms.

In vivo inhibition of AChE activity in the European eel Anguilla anguilla exposed to technical grade fenitrothion

European eel ( Anguilla anguilla) were exposed to sublethal fenitrothion concentrations in a continuous flow-through system for 4 days. Plasma acetylcholinesterase (AChE) activity was evaluated after 2, 8, 12, 24, 32, 48, 56, 72 and 96 h pesticide exposure. AChE activity in the plasma of the eel decreased as concentration of fenitrothion increased. Pesticide induced significant inhibitory effects on the AChE activity of A. anguilla ranging from 51% inhibition at sublethal concentration of 0.02 ppm to 57% inhibition at sublethal concentration of 0.04 ppm. Eel were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Following 1 week of recovery, the AChE activity for those animals previously exposed to fenitrothion was still different from the controls. Animals transferred to clean water showed plasma AChE activities reduced in a 34 and 51% when previously exposed to 0.02 and 0.04 ppm pesticide, respectively. This is probably due because regeneration of the enzyme is mainly by the novo synthesis after exposure to organophosphates and levels need a large extent to recover.

Response and Recovery of Brain Acetylcholinesterase Activity in the European Eel,Anguilla anguilla,Exposed to Fenitrothion

European eel (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations in a continuous flow-through system for 4 days. Brain acetylcholinesterase (AChE) activity was evaluated after 2, 8, 12, 24, 32, 48, 56, 72, and 96 h pesticide exposure. Results indicated that AChE activity in eel brains decreased as the concentration of fenitrothion increased. The pesticide induced significant inhibitory effects on the AChE activity ofA. anguilla,ranging from >40% inhibition at a sublethal concentration of 0.02 ppm to >60% inhibition at a sublethal concentration of 0.04 ppm. Eel were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Samples were removed at 8, 12, 24, 48, 72, 96, 144, and 192 h and eel brain AChE activity was evaluated. Following 1 week of recovery, the AChE activity of those animals previously exposed to 0.02 and 0.04 ppm fenitrothion was still different from that of the controls. So, the AChE activity of eel brains at the end of the recovery phase remained significantly depressed.

Inhibition of Gill Na+,K+-ATPase Activity in the Eel,Anguilla anguilla,by Fenitrothion

European eels (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations (0.02 and 0.04 mg/liter) in a continuous flow-through system for 4 days. Gill Mg2+- and Na+,K+-ATPase activities were evaluated after 2, 8, 12, 24, 32, 48, 56, 72, and 96 h of pesticide exposure. Results indicated that ATPase activity in gill tissue decreased as concentration of fenitrothion increased. Pesticide induced significant inhibitory effects on the Na+,K+-ATPase activity ofA. anguilla,ranging from >56% inhibition at a sublethal concentration of 0.02 ppm to >73% inhibition at a sublethal concentration of 0.04 ppm. Eels were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Samples were removed at 8, 12, 24, 48, 72, 96, 144, and 192 h and eel gill ATPase activity was evaluated. Following 1 week of recovery, the Na+,K+-ATPase activity for those animals previously exposed to 0.04 ppm fenitrothion was still different from that of the controls.

Inhibition of acetylcholinesterase in the australian freshwater shrimp (Paratya australiensis) by profenofos

Profenofos induced significant inhibitory effects on the AChE activity of Paratya australiensis ranging from >40% inhibition at sublethal concentrations of 0.1 to 1.0 μg/L to >80% inhibition at lethal concentrations of ≥10 μg/L. Sublethal chronic exposure (21 d) at a concentration of 0.15 μg/L caused persistent reduction in AChE activity of up to 60%, whereas recovery of AChE activity to normal levels from a 24-h exposure to 0.1 μg/L profenofos required less than 9 d. Shrimp were exposed to 0.1 μg/L profenofos for 24 h and then allowed a period of recovery in pesticide-free water; at the end of this treatment the AChE activity of affected shrimp approached control level. Subsequent 24-h exposures with intermittent stay in pesticide-free water for the same duration as the initial recovery phase resulted in greater inhibition in AChE activity as compared to the initial 24-h exposure. Furthermore, the AChE activity of shrimp at the end of the recovery phases remained significantly depressed.

The effects of diflubenzuron (Dimilin®) on selected mayflies (heptageniidae) and stoneflies (peltoperlidae and pteronarcyidae)

AbstractTwo types of laboratory toxicity tests (exposure in water and feeding) were conducted to determine the effects of diflubenzuron (DFB) on nontarget aquatic insects. The mayflies Cynygmula subaequalis, Stenacron interpunctatum, Stenonema meririvulanum, and Stenonema femoratum (Heptageniidae) and the stonefly Peltoperla arcuata (Peltoperlidae) were exposed to DFB in water for 96 h, then transferred to pesticide‐free water and observed for 36 d. The mayflies were exposed to 0, 0.6, 5.6, 55.7, or 557.2 ppb and the stoneflies to 0, 1.0, 10.2, 101.5, or 1,015 ppb DFB in water. The mayflies were found to be sensitive to DFB in water at concentrations as low as 0.6 ppb. The stonefly was less sensitive to DFB in water. In our feeding studies, Peltoperla arcuata and Pteronarcys proteus (Pteronarcyidae) were fed DFB‐treated yellow poplar leaves for 24 d, then observed for 60 and 90 d, respectively. Survival of treated Peltoperla was significantly different from the controls at day 60. Survival of treated Pteronarcys was not significantly different from the controls during the 90‐d test period, although the low number of molts that occurred during that time may have influenced these results. Future studies should use early life stages that coincide with leaf fall, when treated leaves would be introduced to headwater streams. The life histories of many aquatic insects are timed to make maximum use of leaf detritus as a food base. Introduction of DFB‐treated leaves to headwater streams may adversely affect these organisms.

Food utilization in the fishChauna striatus exposed to sublethal concentrations of DDT and methyl parathion

Sublethal concentrations of DDT and methyl parathion (MP) in the medium significantly affected the rates of feeding, absorption and conversion inChanna striatus. Fish exposed to 250 ppb DDT or MP consumed 23 or 50% less food than those exposed to pesticide-free water. Correspondingly, absorption rate also decreased from 120 cal/g live fish/day in the control to 88 and 59 cal/g/day in those exposed to 250 ppb DDT and MP. Efficiency to convert the absorbed food into body substance dropped from 30% in the control to 6 and 12% in the 250 ppb DDT and MP groups. Metabolic rate of the control averaged to 84 cal/g/day; whereas exposure to DDT did not significantly affect the metabolic rate, a concentration of 250 ppb MP depressed the rate to 52 cal/g/day.

Biomagnification of p, p'-DDT and methoxychlor by bacteria.

Aerobacter aerogenes and Bacillus subtilis accumulated p, p'-DDT and methoxychlor directly from water. Uptake of both (14)C-labeled organochlorine insecticides was rapid; 80 to 90% of the 24-h residues were reached within 30 min. Total cellular residues varied linearly with concentrations of DDT and methoxychlor in water ranging from 0.5 to 5.0 mug/liter. The residue magnification factors from water were between 1,400- to 4,300-fold, but were independent of insecticide concentrations in water. When the insecticide-exposed microbial cells were washed with pesticide-free water, DDT residues were 45% in A. aerogenes and 30% in B. subtilis, whereas the methoxychlor level decreased nearly 75% in both organisms. Subsequent washing did not further reduce the insecticide residue. Autoclave-killed bacteria also rapidly adsorbed DDT and methoxychlor from water and, in some instances, residues were higher than in the living cells. Molecular polarity and lipid solubility appear to influence the retention of the organochlorine insecticides by bacterial cells.

Biomagnification of p, p′-DDT and Methoxychlor by Bacteria

Aerobacter aerogenes and Bacillus subtilis accumulated p, p'-DDT and methoxychlor directly from water. Uptake of both (14)C-labeled organochlorine insecticides was rapid; 80 to 90% of the 24-h residues were reached within 30 min. Total cellular residues varied linearly with concentrations of DDT and methoxychlor in water ranging from 0.5 to 5.0 mug/liter. The residue magnification factors from water were between 1,400- to 4,300-fold, but were independent of insecticide concentrations in water. When the insecticide-exposed microbial cells were washed with pesticide-free water, DDT residues were 45% in A. aerogenes and 30% in B. subtilis, whereas the methoxychlor level decreased nearly 75% in both organisms. Subsequent washing did not further reduce the insecticide residue. Autoclave-killed bacteria also rapidly adsorbed DDT and methoxychlor from water and, in some instances, residues were higher than in the living cells. Molecular polarity and lipid solubility appear to influence the retention of the organochlorine insecticides by bacterial cells.

Effects of cypermethrin on haematological parameters of African freshwater catfish, Clarias gariepinus

The effect of cypermethrin on the haematological parameters of Clarias gariepinus was studied using a two factor complete randomised design with five exposure concentrations and a control. The expo-sure time was 14 days in cypermethrin and 14 days in pesticide free water. Blood samples were col-lected and analysed for Packed Cell volume (PCV), Haemoglobin (Hb), Red blood cell count (RBC),Erythrocyte Sedimentation Rate (ESR), platelet count, White blood cell count (WBC), Mean corpuscular haemoglobin concentration (MCHC), Mean corpuscular haemoglobin volume (MCV) and Mean corpuscular haemoglobin (MCH). In most of the exposure concentrations, the values of PCV, Hb and RBC in the exposure (14 days) and withdrawal periods (14 days) for all concentrations were raised above that of control. Exposure to the chemical caused significant changes (p&lt; 0.05) in the haematological parameters. The responses of RBC indices (MCHC, MCV and MCH) varied widely during the periods; but did not differ (p&gt;0.05) at the exposure period. ESR of the fish increased during the exposure period, decreased at the first week of withdrawal but increased in the fourth week. There were no significant differences (p&gt;0.05) in the ESR, leucocrit and oxygen carrying capacity variable at the various concentrations of cypermethrin and exposure period.Key Words: Cypermethrin, blood parameters, pyrethroid insecticides, Clarias gariepinus

1664. Microsomal disposal of carbamates: Oonnithan, E. S. & Casida, J. E. (1968). Oxidation of methyl- and dimethylcarbamate insecticide chemicals by microsomal enzymes and anticholinesterase activity of the metabolites. J. agric. Fd Chem.16, 28

In this study, the effects of sublethal concentrations of the carbamate carbaryl on the cholinesterase (ChE) and carboxylesterase (CES) activities present in the oligochaete Lumbriculus variegatus and in the pigmented Biomphalaria glabrata gastropod were investigated. The results showed that ChE activity from both species was inhibited by in vivo and in vitro exposure to carbaryl, with EC50 and IC50 values approximately 20 times lower for the oligochaete than for the gastropod. On the other hand, the recovery process in uncontaminated media was more efficient in oligochaetes than in snails. Thus, in only 2 h the oligochaetes showed no inhibition with respect to control values whereas the snails did not reach control values even after 48 h of being in pesticide-free water. CES activity was investigated in whole body soft tissue homogenates using three different substrates: p-nitrophenyl butyrate, 1-naphthyl acetate (NA) and 2-NA. In addition, the presence of multiple CES isozymes in L. variegatus and B. glabrata extracts, with activity towards 1- and 2-NA, was confirmed by native polyacrylamide electrophoresis. In both species, the activities measured using the naphthyl substrates were higher than the activity towards p-nitrophenyl butyrate. In addition, B. glabrata showed a higher CES activity than L. variegatus independently of the substrate used. In L. variegatus, in vivo CES activity towards the different substrates was less sensitive to carbaryl inhibition than ChE activity. In contrast, in B. glabrata, CES activity towards p-nitrophenyl butyrate was inhibited at lower insecticide concentrations than ChE. The results of this study contribute to the knowledge of the sensitivity of non-target freshwater invertebrate Type B-esterases towards pesticides.