Comparing toxicity endpoints on Lecane quadridentata (Rotifera: Monogononta) exposed to two anticholinesterases pesticides

Abstract

Toxicity tests were performed on the freshwater rotifer Lecane quadridentata exposed to the pesticides carbaryl and methyl parathion (lethal, sublethal, and chronic) to compare the sensitivity between different endpoints: (a) 48-h mortality; (b) 30-min in vivo inhibition of esterase activity; (c) 5-day inhibition of the instantaneous growth rate. The emphasis of this work was to find the most appropriate endpoint to evaluate the toxicity of these pesticides in view of their sensitivity, duration, and ecological relevance. The comparison between the three toxicity tests show that the 5-day chronic tests have the lowest EC50 (2.22 and 6.6 mg/L), lowest-observed-effect concentration (2.5 and 2.5 mg/L), and no-observed-effect concentration (1.0 and 1.2 mg/L) values for carbaryl and methyl parathion, respectively. This indicates that the estimate of the instantaneous rate of natural increase r is the most sensitive endpoint regarding the toxicity of these pesticides. This sensitivity might be due to the effect on reducing the growth potential form the first generation on. Lethal and sublethal tests are closely related, suggesting that the immediate effect after inhibition of esterases is death. In general, the sensitivity of L. quadridentata is similar to other species of rotifers exposed to methyl parathion. Therefore, the 5-day chronic toxicity test with the freshwater rotifer L. quadridentata should be considered a good candidate to evaluate the effect of anticholinesterase pesticides, due to its high sensitivity and ecological relevance.

Reduced expression of exocytotic proteins caused by anti-cholinesterase pesticides in Brachionus calyciflorus (Rotifera: Monogononta)

“…In the cladocerans Daphnia pulex (Dodson et al, 1995;Hanazato and Hirokawa, 2004) and D. magna (Hanazato and Yasuno, 1987;Fernández-Casalderrey et al, 1995), organophosphate and carbamate pesticides alter their population dynamics, disrupting structure and function of the aquatic community. The same effect can be observed in the rotifers Brachionus calyciflorus, B. angularis, and B. patulus exposed to methyl-parathion (Fernández-Casalderrey et al, 1993;Flores et al, 1999;Sarma et al, 2001;Flores et al, 2004) and the rotifer Lecane quadridentata exposed to carbaryl and methyl-parathion (Pérez-Legaspi et al, 2012). Thus, since rotifers are aquatic invertebrates with cholinergic (Nogrady and Alai, 1983;Raineri, 1984;Pineda-Rosas et al, 2005), catecholaminergic (Kotikova 1995), and serotoninergic (Kotikova et al, 2005) nervous system, there are susceptible to toxic effects of these pesticides in the aquatic environment.…”

“…The test design included a negative control (EPA medium without toxic), a solvent acetone control, and five different concentrations (0.5, 1, 5, 10 and 20 mg/l) of each pesticide evaluated, in a final volume of 1 ml per test, in triplicate. Concentrations series were established according the LC50 values at 48-hours of exposure for carbaryl (13.72 mg/l) and methyl-parathion (9.49 mg/l), reported previously for the rotifer L. quadridentata (Pérez-Legaspi et al, 2012). Eppendorf tubes with rotifers were centrifuged twice at 14,000 rpm for 10 minutes at 4° C, placing them in an ice bath to maintain the integrity of the pellet with rotifers, eliminating the supernatant with a micropipette blocking the hole in the tip with a 54 µm mesh to prevent aspiration of the rotifers.…”

“…Pesticides such as Methyl-parathion from agricultural run-off are capable of altering the structure of the aquatic community, decreasing biodiversity of benthic macroinvertebrates (Egler et al, 2012). The toxicity of these pesticides is not specific to the target organism, although they are designed to inhibit the activity of acetylcholinesterase (AChE), disabling hydrolysis of the neurotransmitter acetylcholine (ACh) leading to its accumulation in the synapse cholinergic neuromuscular junctions, and causing various neurotoxic effects by the overstimulation of this system (Cranmer, 1986;Relyea and Mills, 2001;Garcia et al, 2003;Newman and Unger, 2003;Nimmo and McEwen, 2009;Pérez-Legaspi et al, 2012). Other adverse effects by methyl-parathion involve peroxidation of lipids, protein oxidation, and damage to DNA by oxidative stress by reactive oxygen species .…”

Adverse Effects of Herbicides on Freshwater Zooplankton

“…This value is 6.5-fold higher than the esterase inhibition NOEC value for glyphosate and 2-fold higher than the Faena® esterase inhibition NOEC value obtained by Domínguez-Cortinas et al (2008). On the other hand, the US EPA (1986) has established a value of 700 μg/L of glyphosate for drinking water, which according to Domínguez-Cortinas et al (2008) esterase inhibition results may represent a risk (LOEC = 62 μg/L, EC50 = 280 μg/L) especially when we consider the ample presence of acetylcholinesterases in the test organisms (Pérez-Legaspi et al, 2011). Daphnia magna (C) 26-h LC50 = 3.6 " " " 48-h LC50 = 9.4 " " " 48-h EC50 = 3.6 " " " 24h,48h EC50 > 39 " " " 48-h LC50 = 6.9 MATC = 0.14-0.25 Lethal toxicity tests with freshwater invertebrates are based on standard protocols which are simple, reproducible, and with certain ecological relevance.…”

“…They are valuable tools to estimate the adverse effect of single chemicals in short periods of exposure (usually 24 and 48 h), with or without food. The most common evaluation parameter is the death or immobility which is represented by the median lethal toxicity (LC50) or the median effect concentration (EC50) (Sarma et al, 2001;Pérez-Legaspi et al, 2011). The cladocerans (Daphnia sp., Ceriodaphnia sp.…”