Effects of dimethoate on snail B-esterase and growth as a function of dose, time and exposure route in a laboratory bioassay

International audienceThe aim was to study the effects of dimethoate on enzymatic targets and on the growth of Helix aspersa for different times and modes of exposure under laboratory conditions. Young snails were exposed to increasing dimethoate concentrations in the food (D. exp) or in an artificial substrate (S. exp) for 1, 2, 7 and 14 days. Both acetylcholinesterase (AChE) and carboxylesterase (CaE) activities were measured in the foot of the snails for each concentration and exposure time tested. Growth was evaluated after 7 days of exposure. AChE inhibition, dose-dependent for all lengths of exposure, was stronger in S. exp. AChE was more sensitive than CaE for both modes of exposure. IC50-7 days was 38.3 mug g(1) in D. exp and 11.7 mug g(1) in S. exp for AChE and was higher than 150 mug g(1) in two exposure modes for CaE. AChE activity decreased from the first day to reach maximum inhibition after 7 days of exposure. As noted for B-esterase activities, growth inhibition was stronger in S. exp and was only significant for AChE inhibition of >90%. The present results show that AChE activity could be used to give early warning of toxic effects of dimethoate in terrestrial gastropods

Bioaccumulative and conchological assessment of heavy metal transfer in a soil-plant-snail food chain

<p>Abstract</p> <p>Background</p> <p>Copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) can pose serious threats to environmental health because they tend to bioaccumulate in terrestrial ecosystems. We investigated under field conditions the transfer of these heavy metals in a soil-plant-snail food chain in Banat area, Romania. The main goal of this paper was to assess the Roman snail (<it>Helix pomatia</it>) usefulness in environmental monitoring as bioindicator of heavy metal accumulation. Eight sampling sites, selected by different history of heavy metal (HM) exposure, were chosen to be sampled for soil, nettle leaves, and newly matured snails. This study also aimed to identify the putative effects of HM accumulation in the environment on phenotypic variability in selected shell features, which included shell height (SH), relative shell height (RSH), and whorl number (WN).</p> <p>Results</p> <p>Significantly higher amounts of HMs were accumulated in snail hepatopancreas and not in foot. Cu, Zn, and Cd have biomagnified in the snail body, particularly in the hepatopancreas. In contrast, Pb decreased when going up into the food chain. Zn, Cd, and Pb correlated highly with each other at all levels of the investigated food chain. Zn and Pb exhibited an effective soil–plant transfer, whereas in the snail body only foot Cu concentration was correlated with that in soil. There were significant differences among sampling sites for WN, SH, and RSH when compared with reference snails. WN was strongly correlated with Cd and Pb concentrations in nettle leaves but not with Cu and Zn. SH was independent of HM concentrations in soil, snail hepatopancreas, and foot. However, SH correlated negatively with nettle leaves concentrations for each HM except Cu. In contrast, RSH correlated significantly only with Pb concentration in hepatopancreas.</p> <p>Conclusions</p> <p>The snail hepatopancreas accumulates high amounts of HMs, and therefore, this organ can function as a reliable biomarker for tracking HM bioavailability in soil. Long-term exposure to HMs via contaminated food might influence the variability of shell traits in snail populations. Therefore, our results highlight the Roman snail (<it>Helix pomatia</it>) potential to be used in environmental monitoring studies as bioindicator of HM pollution.</p

Do metal-rich plants deter herbivores? A field test of the defence hypothesis.

Some plant species growing on metalliferous soils are able to accumulate heavy metals in their shoots up to very high concentrations, but the selective advantage of this behaviour is still unknown. The most popular hypothesis, that metals protect plants against herbivores, has been tested several times in laboratory conditions, with contradictory results. We carried out the first large-scale test of the defence hypothesis in eight natural populations of the model Zn hyperaccumulator Thlaspi caerulescens J. and C. Presl (Brassicaceae). In two climatic regions (temperate, Belgium-Luxembourg, and Mediterranean, southern France), we worked in metalliferous and in normal, uncontaminated environments, with plants spanning a wide range of Zn concentrations. We also examined the importance of glucosinolates (main secondary metabolites of Brassicaceae) as antiherbivore defences. When exposed to natural herbivore populations, T. caerulescens suffered lower herbivory pressures in metal-enriched soils than in normal soils, both in Belgium-Luxembourg and in southern France. The trapping of gastropods shows an overall lower population density in metalliferous compared to normal environments, which suggests that herbivory pressure from gastropods is lower on metalliferous soils. In addition, foliar concentration of glucosinolates was constitutively lower in all populations from metal-enriched soils, suggesting that these have evolved towards lower investment in organic defences in response to lower herbivory pressure. The Zn concentration of plants had a protective role only for Belgian metallicolous plants when transplanted in normal soils of Luxembourg. These results do not support the hypothesis that Zn plays a key role in the protection of T. caerulescens against enemies. In contrast, glucosinolates appear to be directly involved in the defence of this hyperaccumulator against herbivores.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Ciclo de vida de Dysopeas muibum (Mollusca, Subulinidae) em laboratório: efeito do isolamento sobre padrões biológicos e conquiliomorfométricos

O conhecimento dos aspectos biológicos e morfológicos dos moluscos terrestres é importante para o desenvolvimento de medidas de controle de pragas e de estratégias de conservação de espécies. O presente trabalho teve como objetivo caracterizar os padrões de biologia e conquiliomorfometria de Dysopeas muibum Marcus & Marcus, 1968 e verificar o efeito do isolamento sobre seu ciclo de vida e a morfometria da concha, em condições de laboratório. Foi realizado o acompanhamento do crescimento da concha, da liberação de filhotes e da mortalidade de 80 moluscos, dos quais 40 foram mantidos isolados e 40 agrupados (10 moluscos por grupo) em condições naturais de temperatura, umidade relativa e fotoperíodo, desde o nascimento até 180 dias de vida, quando então foram aferidas as medidas da concha. Os moluscos foram criados em terrários plásticos vedados com tecido de algodão e elástico, tendo como substrato terra vegetal esterilizada e alimentados com ração para frangos enriquecida com carbonato de cálcio. Foi verificado que os indivíduos possuem a concha pequena, alongada e são capazes de se reproduzir por autofecundação. Possuem crescimento indeterminado, iteroparidade, baixa mortalidade antes e após a maturidade sexual e a fecundidade aumenta de acordo com o tamanho corporal. O isolamento atuou na fecundidade, embora não tenha influenciado o crescimento, o alcance da maturidade sexual, a relação crescimento-reprodução, a mortalidade e a conquiliomorfometria