Main Speciation Research Articles

Total phosphorus speciation and transport flux dynamics driven by tidal variations in the Shuidong Bay coastal water during summer, China

Phosphorus (P) is a vital nutrient for the growth of marine organisms. Tidal cycle had major influence on various biogeochemical parameters of the bay and changed nutrients input with the ebb and flow of the tide. Seawater was collected by synchronous continuous observation during summer in 2021, to investigate tide drives total phosphorus (TP) variation on the concentration, speciation and exchange flux between Shuidong Bay (SDB) and South China Sea (SCS). Results indicated that there was significant tidal variation in exchange flux of TP between SDB and SCS. DIP and DOP were the main speciation of TDP in different tidal periods, accounting for 53.9 % and 46.1 %TP flowed from SCS to SDB, and monthly exchange flux was about 21.26 t. This study provides new insights in P tidal cycling across the semi-enclosed bay-coastal water continuum, which was implications for understanding P biogeochemical process and primary production dynamics in coastal water.

Speciation analysis and toxicity evaluation of arsenolipids-an overview focusing on sea food.

Arsenic, which can be divided into inorganic and organic arsenic, is a toxic metalloid that has been identified as a human carcinogen. A common source of arsenic exposure in seafood is arsenolipid, which is a complex structure of lipid-soluble organic arsenic compounds. At present, the known arsenolipid species mainly include arsenic-containing fatty acids (AsFAs), arsenic-containing hydrocarbons (AsHCs), arsenic glycophospholipids (AsPLs), and cationic trimethyl fatty alcohols (TMAsFOHs). Furthermore, the toxicity between different species is unique. However, the mechanism underlying arsenolipid toxicity and anabolism remain unclear, as arsenolipids exhibit a complex structure, are present at low quantities, and are difficult to extract and detect. Therefore, the objective of this overview is to summarize the latest research progress on methods to evaluate the toxicity and analyze the main speciation of arsenolipids in seafood. In addition, novel insights are provided to further elucidate the speciation, toxicity, and anabolism of arsenolipids and assess the risks on human health.

Geographical and ecological drivers of coexistence dynamics in squamate reptiles

AbstractAimSpecies richness varies widely across space and is determined by underlying factors that drive species coexistence. Such factors include the speciation process (sympatric vs. allopatric), time since divergence, geographic context and intrinsic properties of the organisms. We model for the first time the coexistence dynamics of lizards and snakes across broad temporal and spatial scales, investigating whether an increase in niche divergence, dispersal abilities and inhabiting islands or continents affect their probability of coexistence.LocationGlobal.Time periodCenozoic.Major taxa studiedSquamata.MethodsWe used 447 sister species pairs, their age since divergence, their level of spatial (sympatric or allopatric) and niche overlap and geographical setting (islands or continents) to fit probabilistic models of species coexistence. We measured morphological traits to quantify niche divergence and used range and body size as proxies for dispersal ability. We applied a model‐comparison framework in lizards and snakes separately to evaluate which factors best explained their coexistence dynamics.ResultsAllopatric speciation is the main speciation mode in snakes but we did not find evidence to favour one speciation mode in lizards. In snakes, sympatric pairs tend to occur on islands and to be more different in body size. On the contrary, dispersal ability shaped the coexistence of lizards, where species were more likely to coexist when they have higher dispersal abilities.Main conclusionsDistinct patterns and mechanisms underlie species coexistence within the order Squamata. Snake coexistence is preferentially produced by secondary sympatry favoured by niche divergence and is more likely to occur in more restricted geographical settings (islands vs. continents). Coexistence in lizards is strongly influenced only by dispersal abilities, but the high heterogeneity of processes simultaneously shaping the distribution of different lizard lineages might have masked specific coexistence signals, and future work should compare coexistence dynamics between clades (e.g. families).

Selenium distribution, translocation and speciation in wheat (Triticum aestivum L.) after foliar spraying selenite and selenate

Given the wide–spread consumption of wheat, the production of selenium (Se)–enriched wheat grain may be an effective method to increase the dietary Se intake in many Se–deficient areas. Herein, we biofortified wheat (Triticum aestivum L.) via the foliar spraying of selenate or selenite at low or high rate, and investigated the resulting Se distribution in different wheat parts and the crucial parts involved in grain Se accumulation. Results showed that Se concentration in grain after selenite spraying was 1.5 times higher than that of selenate. Grain Se accumulation was largely affected by leaves Se and the transfer of Se from node1 to internode1. Furthermore, the main speciation of Se in wheat grain was the organic Se. In addition, the optimal dosage was 15 g ha−1. In summary, foliar spraying 15 g ha−1 of Se is an effective and safe agronomic biofortification practice.

Variation of mercury fractionation and speciation in municipal sewage treatment plant: effects of mercury on the atmosphere.

The speciation of mercury in various processing units of sewage treatment in autumn and winter were studied to understand the conversion and fate of mercury. The results show that the average concentrations of total mercury (THg) in the influent were 130.5 ± 69.8ng/L and 231.3 ± 107.2ng/L in autumn and winter, respectively, and the particulate mercury was the main speciation (accounting for 59.3% and 86.9%, respectively). The proportion of dissolved mercury increased after treatment, and the total removal efficiencies of THg were 78.9% and 90.8%, respectively. The release of mercury into the atmosphere during wastewater treatment was studied for the first time. The dissolved gaseous mercury levels in the influent in autumn and winter were 0.60 ± 0.40ng/L and 0.34 ± 0.21ng/L, respectively. The average gaseous element mercury concentration in aerobic tank air was 6.34 ± 0.49ng/m3. The estimated mercury from aeration was 6.4kg per year in China. The dissolved gaseous mercury will be released to the air if the sewage treatment plant is open-air. Closed sewage treatment and collection of waste gas treatment can reduce the influence of released mercury. Mercury releases into the atmosphere in the process of sewage treatment are one of the fates of mercury in sewage. Closed sewage treatment and collection of waste gas treatment are necessary to reduce the influence of released mercury. The reactive mercury levels in the influents of autumn and winter were 1.28 ± 0.49ng/L and 1.96 ± 0.43ng/L, and these levels account for a small proportion of THg, only 1.7% and 0.8%. Hg2+ were released by the degradation of organic matter in the secondary biological treatment. The THg levels in dehydrated sludge were higher than those in biochemical sludge but lower than the maximum limit of THg in agricultural sludge.

Study on the speciation of arsenic in the genuine medicinal material honeysuckle

Abstract Arsenic (As) accumulated in genuine medicinal materials will not only deteriorate the original medicinal properties of the medicinal materials but also harm the eater’s body. In this study, inductively coupled plasma mass spectrometry (ICP-MS) technology was used to investigate the total As content of honeysuckle in four regions, namely Fengqiu, Henan, Xinmi, Shandong, and Julu, Hebei, as well as the speciation and content of As in the roots, stems, and leaves of honeysuckle. This research shows that the total As content of honeysuckle in the four regions was 0.25–0.3 mg/kg. At 1.5 mol/L H3PO4, 200 W, we performed ultrasonic extraction for 30 min at 60°C and adopted high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) to analyze the As speciation of honeysuckle plants. The soil As speciation mainly exists in the form of As(v). In the medicinal part of honeysuckle, the amount of different As speciation is ranked in the descending order as As(v) > As(iii) > dimethyl As acid > monomethyl As acid > AsC. As(v) is the main speciation, accounting for 64.5% of the total, followed by the most toxic As(iii), which is 18.8%. As(v) absorbed by the root system of honeysuckle from the soil tends to transform to As(iii) when transported upwards, and the transformation process mainly occurs in the roots.

Genetic diversity of Oxytropis section Xerobia (Fabaceae) in one of the centres of speciation.

The genetic diversity and phylogenetic relationships of Oxytropiscaespitosa, O.grandiflora, O.eriocarpa, O.mixotriche, O.nitens, O.peschkovae and O.triphylla, section Xerobia subgenus Oxytropis, in one of the main speciation centres of the genus Oxytropis (Baikal Siberia and adjacent territories of Northeastern Mongolia) were studied based on sequence analysis of the psbA-trnH, trnL-trnF and trnS-trnG intergenic spacers of cpDNA, as well as the ITS nrDNA. Most populations are characterized by a high level of chloroplast genetic diversity (h varied from 0.327 to 1.000 and π from 0.0001 to 0.0090) due to the ancient origin for some species and to hybridization and polyploidy for others. 67 haplotypes were identified, of which six were shared. Phylogenetic relationships among species could not be satisfactorily resolved. Only the haplotypes of O.triphylla formed a group with rather high support. Probably, O.caespitosa, O.grandiflora, O.mixotriche and O.nitens constitute a single genetic complex. As regards the ITS nrDNA polymorphism, we detected only two ribotypes (RX1, RX2). Both were found in O.caespitosa, O.eriocarpa, O.mixotriche and O.peschkovae, while RX1 was present in O.nitens and O.triphylla, RX2 in O.grandiflora. The absence of diagnostic species-specific variants for the markers studied, together with the sharing of cpDNA haplotypes and nrDNA ribotypes between species, and the resulting polytomies on the phylogenetic trees, confirm the hypothesis on the hybrid origin of some of them. Obviously, the reproductive barriers within the sect. Xerobia are weak. However, morphological differences between the species of the sect. Xerobia are clearly pronounced, even when they grow in sympatry.

Genomogenesis of the Plague Bacteria Yersinia pestis as a Process of Mosaic Evolution

The guiding methodological principle of the modern molecular genetic (MG) approach to the problem of speciation of the plague bacteria Yersinia pestis is the saltationist paradigm of horizontal gene transfer. The main speciation events include the insertion of two virulence plasmids specific to Y. pestis, pFra and pPst, into the genome of ancestral psychrophilic saprozoonotic pseudotuberculosis bacteria Y. pseudotuberculosis O:1b, as well as inactivation/deletion of genes that have lost their functions. An alternative ecological approach suggests the “Darwinian” mechanism of the plague bacterium genome formation in the temperature-continuous (5–37°C) environment, i.e., the Tarbagan marmot–marmot flea (Marmota sibirica–Oropsylla silantiewi) parasitic system, which demonstrates intermediate properties between the habitats of progenitor and derivative species. In accordance with the ecological scenario of the plague origin, the evolutionary fate of 18 well-studied plague bacterium genes and gene structures was interpreted. It was demonstrated that gradual transformation of the genome of the pseudotuberculosis bacterium into the genome of plague causative agent proceeded according to the principle of mosaic evolution and corresponded to three types of adaptation, i.e., inadaptation, pre-adaptation and neo-adaptation. The prospects for further development of the theory of plague origin are thought to be in the synthesis of MG and ecological approaches.

Release and transformation mechanisms of hazardous trace elements in the ash and slag during underground coal gasification

Underground coal gasification (UCG) is a new coal utilization technology with advantages of high safety and high efficiency. However, the risk of hazardous trace elements (HTEs) in the UCG residue to the underground environment has always been an important issue. In this paper, the UCG sequential transformation products were prepared, and the chemical speciation of hazardous trace elements (Hg, As, Se, Pb, Cr, and Cd) in the UCG products were studied by using a combination of chemical analysis and thermodynamic calculation. Moreover, the risk assessment code (RAC) was introduced to evaluate the risk level of hazardous trace elements to underground environment. The results indicate that during the UCG pyrolysis process, Hg, Pb, Se, and Cd in the Ulanqab coal react with S to form HgS, PbS, SeS, and CdS, respectively. The oxidizable form of Hg (50.00 ± 0.18–66.67 ± 0.23%) and As (78.34 ± 0.37–83.36 ± 0.46%) is the main speciation in 900–1300 °C reduction ash. For the oxidation ash and slag samples, Hg is loaded on the mineral system of Na-Si-O in the form of HgO, and As is combined with the FeAl2O4. Based on the risk assessment code (RAC), Hg, Se and Pb have medium risk level in the coal and semi-coke. Cr and Se in the 900–1200 °C reduction ash can pose high risk on the underground environment. In the oxidation ash and slag, the risk level of HTEs to the environment decreases. The results can provide scientific guidance for the control and treatment of residues in the later-stage of underground coal gasification.

Major, trace and rare earth elements geochemistry of geothermal waters from the Rehai high-temperature geothermal field in Tengchong of China

Major and trace elements geochemistry of high-temperature geothermal waters are important for understanding the subsurface transport and transfer of mass during groundwater circulation. The major constituents and trace elements, including rare earth elements, are discussed to reveal the source of elements and the hydrogeochemical processes occurring in the geothermal waters in the Rehai high-temperature geothermal field in Southwest China. Neutral-alkaline bicarbonate geothermal waters and acid sulfate waters are observed in Rehai due to different genesises. The bicarbonate waters contain higher concentrations of Na, K, Cl, HCO3, Li, Be, F, Sc, Ti, V, Cr, Ga, Rb, Nb, Sb, Cs, W, Tl, Zr and Si and less SO4 than the sulfate waters. The hydrogeochemical analyses show that the recharge of magmatic fluids, mixing with cold water and water-rock interaction affect the concentration of the elements. The geothermal waters and host rock REE chondrite-normalized patterns and the Eu anomalies are inherited from the host rock signature. Negative Ce anomalies may result from oxidative scavenging process of Ce and/or adsorbtion by the precipitation of Fe oxyhydroxides. T, TDS, pH and Fe/Mn minerals all affect the REE concentrations of geothermal waters. Calculations of REE speciation show that in the alkaline waters, Ln(CO3)2- is the major speciation. In the neutral waters, Ln(CO3)2- and LnCO3+ are the main speciation. In the weak acid waters, LnCO3+ is the main speciation and LnSO4+ are the major speciation in the strong acid water.

Behaviors and fate of adsorbed Cr(VI) during Fe(II)-induced transformation of ferrihydrite-humic acid co-precipitates

The mobility of Cr(VI) in the environment is affected by the transformation of ferrihydrite (Fh) and ferrihydrite-humic acid co-precipitates (Fh-HA). However, the impacts of Fe(II)-induced transformation of Fh and Fh-HA on the mobility, speciation and partitioning of associated Cr(VI) remain unclear. In this study, the behaviors of adsorbed Cr(VI) during Fh and Fh-HA aging at 70 °C for 9 days (pH0 = 3.0 and 7.0) in the absence and presence of Fe(II) were studied. Results revealed that the main speciation of Cr(VI) after transformation was non-desorbable Cr and its formation involved the following pathways. Firstly, Fe(II) (0.2 and 2.0 mM) induced the transformation of Fh-HA to hematite and goethite, promoting the structural incorporation of adsorbed Cr into hematite and goethite via complexation. Secondly, under neutral condition (pH0 = 7.0), the low concentration of Fe(II) (0.2 mM) could not reduce completely Cr(VI) to Cr(III) and thus residual Cr(VI) was incorporated into the Cr(III)-Fe(III) co-precipitates. Thirdly, coprecipitated humic acid not only reduced Cr(VI) to Cr(III) via polysaccharide, but also formed complexes with incorporated Cr through carboxylic groups to sequester Cr. Our results demonstrate that Fe(II)-induced transformation of Fh-HA exerts major influences on associated Cr(VI) speciation and partitioning.

Influence of copper element distribution and speciation on the color of Chinese underglaze copper-red porcelain in the Yuan dynasty

A shard of Chinese underglaze copper-red porcelain from the Yuan dynasty (AD 1271–1368) made in the Jingdezhen kiln was measured by synchrotron radiation-induced X-ray fluorescence mapping and X-ray absorption near-edge spectroscopy to investigate the influence of copper element distribution and speciation on the color of porcelain. In black-colored region, copper accumulates at the interface between the body and glaze layers with metallic copper particles as the main speciation. In contrast, Cu is irregularly distributed in the red-colored region with multi-valence speciation. The differences in Cu distribution and speciation in black- and red-colored regions indicate that they are the main factors influencing the different colors of copper-red underglaze porcelain.

Filogeografía, factores históricos y especificidad parásito-hospedador: estudio comparativo de las comunidades de insectos depredadores de bellotas (Curculio spp.) en la Península ibérica y California

Bonal, R., Munoz, A., Aparicio, J.M, Santoro, M., Espelta, J.M. 2019 2019. Phylogeography, historical factors and host-parasite specificity: comparative study of the communities of acorn feeding insects (Curculio spp.) in the Iberian peninsula and California. Ecosistemas 28(1): 15-25. Doi.: 10.7818/ECOS.1543 Host-parasite specificity constitutes one of the main speciation engines in phytophagous insects. The isolation of populations and its temporal persistence may promote local adaptations at the intra-specific level, in the same way that local extinctions and intense gene-flow among populations eliminate them. These adaptations may be the stage previous to speciation. In this study we compare the trophic specificity patterns of the coleoptera of the genus Curculio (specialist parasites of Quercus seeds) between California and the Iberian peninsula. These two zones have nowadays a very similar climate, however, their past climate histories differ. Using DNA taxonomy techniques we found a potential cryptic species of Curculio in the Iberian peninsula, although trophic specialization does not underlay this possible speciation event. At the intra-specific level, californian Curculio showed a much more marked population genetic structure compared to iberian ones, in which genetic depauperation and a posterior intense inter-population gene-flow can be appreciated. These differences, very similar to those found when the Quercus spp. of both zones were compared, point at the existence of a higher number of glacial refugia in California. Despite that a lower inter-population gene-flow prolonged in time could have promoted a higher specialization in California, there were not differences with the Iberian Peninsula in this sense. The marked inter-annual variability of the trophic source (fluctuations of acorn crops not always coincident among Quercus species) may have favoured the lack of a very strict specificity.

In situ arsenic speciation and the release kinetics in coastal sediments: A case study in Daya Bay, South China Sea

In-situ study on arsenic speciation and the release kinetics in marine sediments was scarce. In this study, the distributions of labile As and their speciation in coastal sediments of Daya Bay were obtained by separate diffusive gradients in thin films (DGT) probes. Results showed that the DGT-labile As(V) was the main speciation in surface sediments (from −20 to 0 mm) with a concentration range of 0.07–3.05 μg·L−1, while the labile As(III) was the main speciation in deep layers of sediments (from −100 to −20 mm). In coastal areas, mariculture farms was the most dominated contributor to As(V) contamination in surface sediments. Both the apparent diffusion flux estimation and the DGT induced flux in sediments (DIFS) simulation indicated that As(V) contamination in surface sediments of mariculture, harbor and petrochemical areas suffered the potential risk of As(V) release into the overlying water from sediments. DIFS modeling also found that the sediments of mariculture farms were the main sediment As pools. Linear regression analysis indicated that the mobility of As mainly attributed to the As(V) in sediments.

The migration and transformation regular study of metal manganese in surface soil of Yiwang Industrial Park in Shanxi Province, China

ABSTRACTAll kinds of industries can produce a large amount of the heavy metal Mn emission, especially in the Mn steel plant production process. The assessment of Mn pollution in industrial areas is vital to human health and soil conservation. First, there are 120 samples of 0–5 cm and samples 9 of 0–40 cm of the surface soil collected from outside. Next, the soil column test is applied to study the migration and speciation regularity of Mn in 0–40 cm of soil layer, and then a forecasting model is established to verify and evaluate the Mn pollution in the study area. After the exogenous Mn enters the soil, Mn soon transforms into a more stable form in soil at 0–20 cm depth. But the residual amounts of Mn in deep soil increases with the increase of exogenous Mn. The main speciation of Mn in surface soil includes residual, oxide-bound, and organic-bound forms. Carbonate-bound form is sensitive to the increase of exogenous Mn. The exogenous Mn content has less influence on the content of oxide-bound and organic-bound forms in soils below 20 cm. The prediction model can be used to evaluate the degree of pollution of Mn in surface soil of the study area.

Researching of tritium speciation in soils of “Balapan” site

Speciation of tritium (3Н) in soils from the “Balapan” site in Semipalatinsk are presented in this study. Three interrelated objects were chosen for further study: “Atomic” lake, the Shagan River and an external reservoir. The main speciation forms of 3Н in soil were: 3Н in surface-adsorbed water, 3Н in interlayer water, hydroxylic 3Н, organically bound 3Н and crystalline-bound 3Н.Results will allow an estimation of contamination mechanism to be made, and will also allow the potential for migration and bioavailability of 3Н to be assessed.

Species delimitation of colour polymorphic Cladophorus (Coleoptera: Lycidae) from New Guinea

Cladophorus Guérin-Méneville, 1830 are endemic Papuan net-winged beetles which take part in highly diverse Müllerian mimicry rings. Available specimens were sequenced for cox1–tRNA-Leu–cox2 mitochondrial DNA fragment and the species delimitations were based on the genetic distance, phylogenetic analysis, and morphology. Three earlier described species were identified in the recently collected material and further 10 species are described: C. pallescens sp. nov., C. bicolor sp. nov., C. craterensis sp. nov., C. motykai sp. nov., C. mindikensis sp. nov., C. kailakiensis sp. nov., C. manokwarensis sp. nov., C. haiaensis sp. nov., C. humeralis sp. nov., and C. boceki sp. nov. DNA-based identifications provided some ambiguous results and closely related species could not be robustly delimited using solely molecular data. Additionally, the species limits were based on clearly defined morphological characters and the morphological differentiation was found unlinked from the genetic divergence. Colour patterns cannot be used for identification because all species available in more specimens were polymorphic and followed various local co-mimics. The Papuan fauna of Cladophorus is very diverse and the closely related species regularly occur in limited regions. Differentiation within restricted ranges is therefore considered as the main speciation mode.

Migration and speciation of heavy metal in salinized mine tailings affected by iron mining.

The negative effects of heavy metals have aroused much attention due to their high toxicity to human beings. Migration and transformation trend of heavy metals have a close relationship with soil safety. Researching on migration and transformation of heavy metals in tailings can provide a reliable basis for pollution management and ecosystem restoration. Heavy metal speciation plays an important role in risk assessment. We chose Anshan tailings for our study, including field investigations and laboratory research. Four typical heavy metal elements of mine tailings {Fe (373.89 g/kg), Mn (2,303.80 mg/kg), Pb (40.99 mg/kg) and Cr (199.92 mg/kg)} were studied via Tessier test in vertical and horizontal direction. The main speciation of heavy metals in Anshan tailings was the residual. However, heavy metals have a strong ability for migration and transformation in vertical and horizontal directions. Its tendency to change from stable to unstable speciation results in increasing bioavailability and potential bioavailability. Fe, Mn, Pb and Cr showed different ability in the migration and transformation process (Mn > Pb > Fe > Cr) depending on the characteristics of heavy metals and physicochemical properties of the environment.

Molecular systematics and phylogeography of the genus Echinops (Compositae, Cardueae–Echinopsinae): focus on the Iranian centre of diversification

A molecular phylogeny of the genus Echinops (Asteraceae, Cardueae) based on plastid and nuclear markers is presented. The study focuses on the Iranian representatives of the genus, which constitute a larger part of Echinops. The Bayesian cpDNA tree resulted in a large polytomy. However, the Bayesian ITS tree displayed a well-resolved topology more compatible with the taxonomic treatment generally accepted in Echinops. An ITS network illustrates a close relationship of haplotypes. Mapping diagnostic morphological characters onto the ITS tree revealed a high level of homoplasy among the studied taxa. Except for the life cycle, all other morphological characters evolved many times among the clades and most of them appeared to be of low taxonomical value. Based on the nucleotide polymorphism and haplotypes, the taxonomic status of some taxa was evaluated. The independent status of E. sect. Phaeochaete was confirmed by molecular analyses and morphological characters. The paraphyletic nature of E. sect. Echinops was confirmed. As for the molecular dating, our results suggest that the genus evolved in the early Miocene but the main speciation events took place in the Pliocene-Pleistocene. The biogeographic results do not support any specific ancestral area for Echinops, yet the model states that its current diversity originated in the Irano-Turanian Region and the Eastern Mediterranean region. Some taxonomic changes are suggested, in the synonymy and placement of some taxa.

Interaction of As and Sb in the hyperaccumulator Pteris vittata L.: changes in As and Sb speciation by XANES.

Arsenic (As) and antimony (Sb) are chemical analogs that display similar characteristics in the environment. The As hyperaccumulator Pteris vittata L. is a potential As-Sb co-accumulating species. However, when this plant is exposed to different As and Sb speciation, the associated accumulating mechanisms and subsequent assimilation processes of As and Sb remain unclear. A 2-week hydroponic experiment was conducted by exposing P. vittata to single AsIII, AsV, SbIII, and SbV or the co-existence of AsIII and SbIII and AsV and SbV. P. vittata could co-accumulate As and Sb in the pinna (>1000mgkg(-1)) with high translocation (>1) of As and Sb from the root to the pinna. P. vittata displayed apparent preference to the trivalent speciation of As and Sb than to the pentavalent speciation. Under the single exposure of AsIII or SbIII, the pinna concentration of As and Sb was 84 and 765% higher than that under the single exposure of AsV or SbV, respectively. Despite the provided As speciation, the main speciation of As in the root was AsV, whereas the main speciation of As in the pinna was AsIII. The Sb in the roots comprised SbV and SbIII when exposed to SbV but was exclusively SbIII when exposed to SbIII. The Sb in the pinna was a mixture of SbV and SbIII regardless of the provided Sb speciation. Compared with the single exposure of As, the co-existence of As and Sb increased the As concentration in the pinna of P. vittata by 50-66%, accompanied by a significant increase in the AsIII percentage in the root. Compared with the single exposure of Sb, the co-existence of Sb and As also increased the Sb concentration in the pinna by 51-100%, but no significant change in Sb speciation was found in P. vittata.