Developmental toxicity of metaldehyde in the embryos of Lymnaea stagnalis (Gastropoda: Pulmonata) co-exposed to the synergist piperonyl butoxide

Abstract

Metaldehyde is a widely used molluscicide in countries where damage to crops from slugs and snails is a major problem associated with warm and wet winters. In the UK it is estimated that over 8% of the area covered by arable crops is treated with formulated granular bait pellets containing metaldehyde as the main active ingredient. Metaldehyde is hydrophilic (log Kow=0.12), water soluble (200 mg·L(-1) at 17 °C) and has been detected in UK surface waters in the concentration range of typically 0.2-0.6 μg·L(-1) (maximum 2.7 μg·L(-1)) during 2008-2011. In the absence of chronic data on potential hazards to non-target freshwater molluscs, a laboratory study was conducted to investigate the impact of metaldehyde on embryo development in the gastropod Lymnaea stagnalis (RENILYS strain) and using zinc as a positive control. L. stagnalis embryos were exposed to metaldehyde under semi-static conditions at 20±1 °C and hatching success and growth (measured as shell height and intraocular distance) examined after 21 d. Exposure concentrations were verified using HPLC and gave 21 d (hatching)NOEC and (hatching)LOEC mean measured values of 36 and 116 mg MET·L(-1), respectively (equal to the 21 d (shell height)NOEC and (shell height)LOEC values). For basic research purposes, a second group of L. stagnalis embryos was co-exposed to metaldehyde and the pesticide synergist piperonyl butoxide (PBO). Co-exposure to the PBO (measured concentrations between 0.47-0.56 mg·L(-1)) reduced hatching success from 100% to 47% and resulted in a 30% reduction in embryo growth (shell height) in snail embryos co-exposed to metaldehyde at 34-36 mg·L(-1) over 21 d. In conclusion, these data suggest mollusc embryos may have some metabolic detoxication capacity for metaldehyde and further work is warranted to explore this aspect in order to support the recent initiative to include molluscs in the OECD test guideline programme.

The acute toxicity of the metaldehyde on the climbing perch

“…Massive mucus discharge by the fish is due to the metaldehyde's toxic mode of action causing irreversible damage in the mucous cells of the skin, thus leads to excessive mucus production, and destruction of the mucus cells [30][31]. When the fish died, the mouth and the opercula were wide open and the skin colour of the fish changed from dark to pale.…”

Review of the molluscicide metaldehyde in the environment

“…Studies by Edwards et al 39 and Langan et al 40 showed that exposure of Lumbricus terrestris L. in microcosms to high concentrations of metaldehyde had no effect on mortality, growth or feeding rate. Hallett et al 41 investigated in the laboratory the impact of metaldehyde on embryo development in the pond snail Lymnaea stagnalis. Chronic effects from metaldehyde exposure (high mg L −1 range) on embryo development were observed, however, the authors' suggest that at typical environmental exposures (μg L −1 ) there is a low risk to the early developmental stages of this gastropod mollusc.…”

Inhibition Kinetics of Acetylcholinesterase and Phosphatases by the Active Constituents of Terminalia arjuna and Tamarindus indica in the Cerebral Ganglion of Lymnaea acuminata

“…The use of synthetic or plant molluscicides is the best method of snail control. 11,12 Synthetic molluscicides have created serious environmental hazards arising from contamination of ecosystem and its toxicity to non-target animals. Alternatively, molluscicides activity of plant origin are gaining more acceptance among farmers, as it is ecologically and culturally more acceptable than their synthetic counterpart.…”