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Journal ArticleDOI

Selenium biotransformations in an insect ecosystem: effects of insects on phytoremediation.

01 Jul 2004-Environmental Science & Technology (American Chemical Society)-Vol. 38, Iss: 13, pp 3581-3586
TL;DR: The surprising finding of trimethylselenonium-like species in adult parasitoids and the cocoons from which they emerged suggests that adults and pharates can detoxify excess selenium through methylation and volatilization.
Abstract: Phytoremediation of selenium-contaminated soils may be influenced by higher trophic levels including insects. We examined how selenium affects the behavior, survival, and development of the wasp parasitoid Cotesia marginiventris, parasitizing its natural host, the beet armyworm Spodoptera exigua, feeding on alfalfa, Medicago sativa, irrigated with water containing selenate. X-ray absorption spectroscopy was used to quantify the selenium chemical forms in each trophic level. Alfalfa partially transformed selenate to organoselenium. S. exigua contained only organoselenium, both directly absorbed from M. sativa and transformed from selenate. C. marginiventris cocoons collected shortly after larval emergence contained only organoselenium derived from the host. The surprising finding of trimethylselenonium-like species in adult parasitoids and the cocoons from which they emerged suggests that adults and pharates can detoxify excess selenium through methylation and volatilization. Adult parasitoids do not discriminate against selenium-containing alfalfa, even though alfalfa generates selenium volatiles. Parasitoids raised on selenium-fed larvae emerged later and pupae weighed less than their selenium-free counterparts. We conclude therefore that C. marginiventris can be used to control S. exigua damage to M. sativa being used to remove selenium from soils. Moreover, the presence of such insects may improve phytoremediation by increasing biotransformation of inorganic selenium and release of volatile selenium species.

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Citations
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Journal ArticleDOI
TL;DR: A specific flow of Se is suggested in hyperaccumulator plants over the growing season, from root to young leaves in spring, followed by remobilization from aging leaves to reproductive tissues in summer, and back to roots in the autumn.
Abstract: Summary • Some plants hyperaccumulate selenium (Se) up to 1% of dry weight. This study was performed to obtain insight into whole-plant Se fluxes in hyperaccumulators. • Selenium hyperaccumulators Astragalus bisulcatus and Stanleya pinnata were monitored over two growing seasons for seasonal fluctuations in concentrations of Se and the chemically similar element sulfur (S). The related nonhyperaccumulators Astragalus sericoleucus , Oxytropis sericea and Thlaspi montanum were included for comparison. • In both hyperaccumulators leaf Se decreased from April to October, coinciding with Se hyperaccumulation in flowers and seeds. Root Se levels were lowest in summer. Selenium concentration decreased with leaf age in both hyperaccumulators. Leaf S levels peaked in summer in all plant species, as did Se levels in nonhyperaccumulators. Selenium and S levels tended to be negatively correlated in hyperaccumulators, and positively correlated in nonhyperaccumulators. • These results suggest a specific flow of Se in hyperaccumulator plants over the growing season, from root to young leaves in spring, followed by remobilization from aging leaves to reproductive tissues in summer, and back to roots in the autumn.

199 citations

Journal ArticleDOI
TL;DR: Although Se hyperaccumulation protects plants from herbivory by some invertebrates, it can give rise to the evolution of unique Se-tolerant herbivores and thus provide a portal for Se into the local ecosystem, providing insight into the possible ecological implications of using Se-enriched crops as a source of anti-carcinogenic selenocompounds and for the remediation of Se-polluted environments.

123 citations

Journal ArticleDOI
TL;DR: Basic biokinetic measurements revealed that Se had direct interaction with Hg(II) during dietary assimilation rather than with MeHg and that different Se species had variable effects on Hg assimilation.
Abstract: It is well-known that selenium (Se) shows protective effects against mercury (Hg) bioaccumulation and toxicity, but the underlying effects of Se chemical species, concentration, and administration method are poorly known. In this study, we conducted laboratory studies on a marine fish Terapon jurbua to explain why Hg accumulation is reduced in the presence of Se observed in field studies. When Se and Hg were administrated concurrently in the fish diets, different Se species including selenite, selenate, seleno-dl-cystine (SeCys), and seleno-dl-methionine (SeMet) affected Hg bioaccumulation differently. At high concentration in fish diet (20 μg g−1 normally), selenate and SeCys significantly reduced the dietary Hg(II) assimilation efficiency (AE) from 38% to 26%. After the fish were pre-exposed to dietary selenite or SeMet (7 μg g−1 normally) for 22 days with significantly elevated Se body concentrations, the Hg(II) AEs were pronouncedly reduced (from 41% to 15−26%), whereas the dissolved uptake rate const...

104 citations

Journal ArticleDOI
TL;DR: The effectiveness of selenium (Se) as an arthropod deterrent was investigated under field conditions and it is suggested that invertebrate herbivory may have contributed to the evolution of Se hyperaccumulation.
Abstract: The elemental defense hypothesis proposes that some plants hyperaccumulate toxic elements as a defense mechanism. In this study the effectiveness of selenium (Se) as an arthropod deterrent was investigated under field conditions. Arthropod loads were measured over two growing seasons in Se hyperaccumulator habitats in Colorado, USA, comparing Se hyperaccumulator species (Astragalus bisulcatus and Stanleya pinnata) with nonhyperaccumulators (Camelina microcarpa, Astragalus americanus, Descurainia pinnata, Medicago sativa, and Helianthus pumilus). The Se hyperaccumulating plant species, which contained 1000-14 000 microg Se g(-1) DW, harbored significantly fewer arthropods (c. twofold) and fewer arthropod species (c. 1.5-fold) compared with nonhyperaccumulator species that contained 10-fold lower Se concentrations than their hyperaccumulator hosts. Several arthropod species contained > 100 microg Se g(-1) DW, indicating Se tolerance and perhaps feeding specialization. These results support the elemental defense hypothesis and suggest that invertebrate herbivory may have contributed to the evolution of Se hyperaccumulation.

92 citations

Journal ArticleDOI
13 Apr 2012-PLOS ONE
TL;DR: This study has shown that bees fed selenate were less responsive to sucrose, which may lead to a reduction in incoming floral resources needed to support coworkers and larvae in the field, and reductions in population numbers may occur due to direct toxicity.
Abstract: We know very little about how soil-borne pollutants such as selenium (Se) can impact pollinators, even though Se has contaminated soils and plants in areas where insect pollination can be critical to the functioning of both agricultural and natural ecosystems. Se can be biotransferred throughout the food web, but few studies have examined its effects on the insects that feed on Se-accumulating plants, particularly pollinators. In laboratory bioassays, we used proboscis extension reflex (PER) and taste perception to determine if the presence of Se affected the gustatory response of honey bee (Apis mellifera L., Hymenoptera: Apidae) foragers. Antennae and proboscises were stimulated with both organic (selenomethionine) and inorganic (selenate) forms of Se that commonly occur in Se-accumulating plants. Methionine was also tested. Each compound was dissolved in 1 M sucrose at 5 concentrations, with sucrose alone as a control. Antennal stimulation with selenomethionine and methionine reduced PER at higher concentrations. Selenate did not reduce gustatory behaviors. Two hours after being fed the treatments, bees were tested for sucrose response threshold. Bees fed selenate responded less to sucrose stimulation. Mortality was higher in bees chronically dosed with selenate compared with a single dose. Selenomethionine did not increase mortality except at the highest concentration. Methionine did not significantly impact survival. Our study has shown that bees fed selenate were less responsive to sucrose, which may lead to a reduction in incoming floral resources needed to support coworkers and larvae in the field. If honey bees forage on nectar containing Se (particularly selenate), reductions in population numbers may occur due to direct toxicity. Given that honey bees are willing to consume food resources containing Se and may not avoid Se compounds in the plant tissues on which they are foraging, they may suffer similar adverse effects as seen in other insect guilds.

81 citations

References
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Journal ArticleDOI
28 Nov 2003
TL;DR: Recent advances in the understanding of the plant's ability to metabolize Se into volatile Se forms (phytovolatilization) are discussed, along with the application of phytoremediation for the cleanup of Se contaminated environments.
Abstract: Plants vary considerably in their physiological response to selenium (Se). Some plant species growing on seleniferous soils are Se tolerant and accumulate very high concentrations of Se (Se accumulators), but most plants are Se nonaccumulators and are Se-sensitive. This review summarizes knowledge of the physiology and biochemistry of both types of plants, particularly with regard to Se uptake and transport, biochemical pathways of assimilation, volatilization and incorporation into proteins, and mechanisms of toxicity and tolerance. Molecular approaches are providing new insights into the role of sulfate transporters and sulfur assimilation enzymes in selenate uptake and metabolism, as well as the question of Se essentiality in plants. Recent advances in our understanding of the plant's ability to metabolize Se into volatile Se forms (phytovolatilization) are discussed, along with the application of phytoremediation for the cleanup of Se contaminated environments.

1,243 citations

Reference BookDOI
10 Jun 1994
TL;DR: The authors discusses the biochemical and geological cycling of selenium (Se), its worldwide distribution, and the factors controlling its fate and transport within and between major environmental media, presenting a global assessment of Se's complex environmental behaviour.
Abstract: Discusses the biochemical and geological cycling of selenium (Se), its worldwide distribution, and the factors controlling its fate and transport within and between major environmental media, presenting a global assessment of selenium's complex environmental behaviour. The focus of this work is upon Se management and remediation strategies.

348 citations

Journal ArticleDOI
TL;DR: Selenium prevents several type of chemically induced cancer in animals, and, where more selenium occurs in the environment, human cancer death rates are lower and human heart disease mortality is lower.

341 citations

Book
03 Feb 1998
TL;DR: In this article, federal and state perspectives on regulation and remediation of irrigation-induced selenium problems methods of analysis for the determination of SE in biological, geological and water samples are discussed.
Abstract: Federal and state perspectives on regulation and remediation of irrigation-induced selenium problems methods of analysis for the determination of selenium in biological, geological and water samples analytical detection of selenium in water, soil and plants sequential supplementation of fertilizers on human nutrition and selenium status effects of selenium supplementation of field crops selenium metabolism in grazing ruminants - deficiency, supplementation and environmental implications environmental implications of uses of selenium with animals supplementation of selenium in the diets of domestic animals mass balance approach to selenium cycling through the San Joaquin Valley - from source to river to bay selenium sources and effects of biota in the Green River Basin of Wyoming, Colorado, and Utah selenium and salinity concerns in the Salton Sea area of California selenium cycling in estuarine wetlands - overview and new results from the San Francisco bay selenium accumulation in a wetland channel, Benton Lake, Montant selenite sorption by coal mine backfill materials in the presence of organic solutes pathology of selenium poisoning in fish selenium effects on endangered fish in the Colorado River basin selenium poisoning of fish and wildlife in nature - lessons from 12 real-world experiences magic numbers, elusive lesions - comparative pathology and toxicology of selenosis in waterfowl and mammalian species prediction of lands susceptible to irrigation-induced selenium contamination of water (Part contents)

312 citations

Journal ArticleDOI
TL;DR: The bioavailability, including absorption, transport, metabolism, storage, and excretion, of the different forms of exogenous and endogenous Se are reviewed.
Abstract: Selenium (Se) is at once an essential and toxic nutrient that occurs in both inorganic and organic forms. The biological functions of Se are mediated through at least 13 selenoproteins that contain Se as selenocysteine (Se-cyst). The endogenous synthesis of this amino acid from inorganic Se (selenide Se-2) and serine is encoded by a stop codon UGA in mRNA and involves a unique tRNA. Selenium can also substitute for sulfur in methionine to form an analog, selenomethionine (Se-meth), which is the main form of Se found in food. Animals cannot synthesize Se-meth or distinguish it from methionine and as a result it is nonspecifically incorporated into a wide range of Se-containing proteins. The metabolic fate of Se varies according to the form ingested and the overall Se status of an individual. This paper reviews the bioavailability, including absorption, transport, metabolism, storage, and excretion, of the different forms of exogenous and endogenous Se.

265 citations