Arsenic-speciation in arsenate-resistant and non-resistant populations of the earthworm, Lumbricus rubellus

Langdon, Caroline J.; Meharg, Andrew A.; Feldmann, Jörg; Balgar, Thorsten; Charnock, John; Farquhar, Morag L.; Piearce, Trevor G.; Semple, Kirk T.; Cotter-Howells, Janet

doi:10.1039/b201366p

Cited by 71 publications

(86 citation statements)

References 20 publications

(49 reference statements)

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“…17 However, the fact that AB is only present at low concentrations between 0.5 and 14 mg kg -1 (Table 2) irrespective of the total As body burden (Fig. 3b) suggests that AB formation is not a mechanism by which earthworms at DGC mitigate As toxicity.…”

Section: Discussionmentioning

confidence: 93%

“…As III -sulphur complexes were detected in DGC earthworms by Langdon et al (2002) 17 when the in-situ speciation technique X-ray Absorption Spectroscopy (XAS) was employed. It is possible that the solvent extraction method employed in this study may cause 45 dissociation of As III -sulphur complexes leading to the detection As III alone.…”

Section: Discussionmentioning

confidence: 99%

“…The resistance is more likely due to a second process (Fig. 2, c) whereby As is thought to be sequestered via binding with sulphur-rich metallothionein within the chloragogenous tissue 3,17,31 allowing the continued 15 accumulation of inorganic As (Fig. 3a) in a form that is not biologically reactive 6 .…”

Section: Discussionmentioning

confidence: 99%

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Arsenic biotransformation in earthworms from contaminated soils

et al. 2009

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Two species of arsenic (As) resistant earthworm, Lumbricus rubellus and Dendrodrillus rubidus, their host soils and soil excretions (casts) were collected from 23 locations at a former As mine in 5 Devon, UK. Total As concentrations, measured by ICP-MS, ranged from 255 to 13,080 mg kg -1 in soils, 11 to 877 mg kg -1 in earthworms and 284 to 4221 mg kg -1 in earthworm casts from a subsample of 10 of the 23 investigated sites. The samples were also measured for As speciation using HPLC-ICP-MS to investigate potential As biotransformation pathways. Inorganic arsenate (As V ) and arsenite (As III ) were the only species detected in the soil. As V and As III were also the dominant 10 species found in the earthworms and cast material together with lower proportions of the organic species methylarsonate (MA V ), dimethylarsinate (DMA V ), arsenobetaine (AB) and three arsenosugars. Whilst the inorganic As content of the earthworms increased with increasing As body burden, the concentration of organic species remained relatively constant. These results suggest that the biotransformation of inorganic arsenic to organic species does not contribute to As 15 resistance in the sampled earthworm populations. Quantification of As speciation in the soil, earthworms and cast material allows a more comprehensive pathway for the formation of AB in earthworms to be elucidated. Received (in XXX, IntroductionThe chemistry of As in environmental and biological systems is complex. Whilst inorganic As species are the most prevalent in abiotic environments, the uptake of inorganic As 25 by living organisms can lead to the synthesis of organic As species 1 through biotransformation. The ubiquitous, epegeic earthworm species L. rubellus and D. rubidus are known to inhabit soils highly contaminated with As at the former mine site of Devon Great Consols (DGC), UK. [2][3][4][5] These earthworms 30 are clearly resistant to As toxicity and several potential coping mechanisms have been proposed, yet the underlying mechanism behind this resistance is unknown. Behavioural adaptation, whereby the earthworm avoids contact with the contaminant, 4 is unlikely as earthworms from DGC are known 35 to have elevated As body burdens. 2,4, 5 The biotransformation of highly toxic inorganic As to the less toxic organic species arsenobetaine (AB) has been speculated as a mode of mitigating As toxicity in DGC earthworms. 2,4 An alternative mechanism involves the sequestration of arsenic in the 40 metallothionein-rich chloragogenous tissue which separates the intestine from the coelomic cavity. 3 With this mechanism it is proposed that inorganic As III binds to the sulphur-rich metallothionein thereby sequestering ingested As in a form that is not biologically reactive. The study of As speciation can provide important information on As biotransformation and toxicity and to date a multitude of organic As species have been identified. 7 The occurrence of organic As species and their biotransformation pathways are well documented in marine organisms such as crus...

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

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Arsenic biotransformation in earthworms from contaminated soils

et al. 2009

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“…The presence of As-S complexes in the intestine has been well documented in earthworms. [26] Similarly, previous studies have shown that some metals tend to be concentrated in the midgut where they are stored in the form of granules [27,28] or in lysosomes. [29] Depuration of metals from the gut may occur when these storage structures are excreted from the body.…”

Section: Arsenic Speciation Using X-ray Absorption Spectroscopymentioning

confidence: 99%

Arsenic accumulation, biotransformation and localisation in bertha armyworm moths

Andrahennadi

Pickering

2008

Environ. Chem.

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Environmental context. Insects play an important role in the impact of environmental pollutants such as arsenic. They may accumulate arsenic to high levels, potentially modifying its chemical form, which affects the insects' toxicity to predators such as fish and birds. Here we use synchrotron X-ray techniques to determine the distribution and chemical form of arsenic in larva, pupa and adult of the bertha armyworm moth.Abstract. Insects are important in bioaccumulation and dispersal of environmental contaminants such as arsenic, and biotransformation of arsenic to various chemical forms directly impacts its toxicity to insects and to their predators. In a model study, the toxic effects and biotransformation of arsenic were examined in larvae, pupae and adults of bertha armyworm moth (Mamestra configurata Walker) (Lepidoptera: Noctuidae). A synthetic diet containing 100 µM arsenate caused reduced larval survival and increased pupal stage duration but no effect on pupal weight or larval stage duration. Synchrotron X-ray absorption spectroscopy (XAS) showed that larvae biotransformed dietary arsenate to yield predominantly trivalent arsenic coordinated with three aliphatic sulfurs, modelled as As III -tris-glutathione. Similar species were found in pupae and adults. XAS imaging with micro X-ray fluorescence imaging revealed highly localised arsenic species, and zinc and copper within the gut. The implication of these arsenic species in the diets of predators is discussed.

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“…Methanol-water extractions have been widely used for the extraction of arsenic species from biota samples, including earthworms [14][15][16][17] . Arsenite and arsenate were 60 demonstrated as the main extractable inorganic arsenicals in L. rubellus 15,18 . In most cases arsenobetaine (AB) is present as the primary organic arsenic species with methylarsonate (MA) present at trace levels 14,18 .…”

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confidence: 99%