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To investigate the release and degradation of arsenolipids present in the marine brown macroalga Ecklonia radiata, tissues were collected in various stages of decomposition from intertidal environments, while tissues were also decomposed in laboratory-based microcosms prepared using combinations of autoclaved and natural (non-autoclaved) seawater and sand. Field collected macroalgae samples contained 20–120 μg g−1 total As of which 1–10% were arsenolipids comprising mainly an arsenic hydrocarbon (AsHC; 3–13% of total arsenolipids) and four di-acyl arsenic phospholipids (AsPLs; 86–95%). Additionally, a mono-acyl AsPL was found in all water-column decomposing samples. Arsenolipid concentrations in live tissues were similar to those in tissues decomposing in the water-column (1.3–2.9 μg g−1 dry mass), which were both up to four times higher than those in decomposing tissues collected from intertidal environments (0.7–1.3 μg g−1 dry mass). In the microcosm experiments, the arsenolipid content of E. radiata decreased substantially as decomposition proceeded. In the majority of microcosms, more than 75% of the arsenolipids present initially disappeared within 5 days with only the AsHC persisting until day 60 (the length of the experiment). This study demonstrates that the habitat in which decomposition occurs influences the release and degradation of arsenolipids with the greatest losses occurring when tissues decompose in intertidal environments. Microbial diversity, biomass, and overall activity are thus likely to play important roles in the persistence of arsenolipids in decomposing algae. Refereed/Peer-reviewed

Balanced applications of nitrogen (N), phosphorus (P), and potassium (K) are known to increase grain yield of wheat but the impact of the interactions among N, P, and K on root growth and nitrogen use efficiency (NUE) have not been proven. The aim of this study was to investigate the effect of balanced applications of N, P, and K on the rooting patterns and NUE of wheat. Two glasshouse experiments were conducted. A rhizobox study was used to assess the impact of interactions among N, P, and K fertilisers on total root length, biomass, specific root length, root length density, N use efficiency (NUE), and N uptake efficiency of the shoots (NUpE shoot ) and N nutrition index. In a separate pot study, plants were grown to maturity to confirm the effect of the observed changes in root growth on NUE, NUpE grain , and grain/biomass yield. In the rhizobox experiment when plants were supplied with N+P+K, total root biomass increased approximately six-fold relative to plants grown with N alone or with no fertiliser. Plants exposed to N+P+K had NUpE shoot and NUE values that were five and ten times higher, respectively, than plants that received just fertiliser N. Plants supplied with N+P or N+P+K had N nutrition indices close to one (N-adequate), while plants that only received N had an index of 0.62 (N-deficient). The pot study confirmed that the changes in root length and biomass in plants exposed to N+P+K resulted in significant increases in NUE, NUpE grain , shoot biomass, and grain yield at maturity. Interactions among fertiliser N, P, and K played a critical role in influencing root biomass and length, which was associated with increases in NUE, NUpE shoot and NUpE grain . Refereed/Peer-reviewed

Unicellular algae are ubiquitous in the paddy environments commonly used to cultivate rice (Oryza sativa) where they play a range of beneficial and detrimental roles in rice production. This study investigated whether the presence of two common metal oxide engineered nanoparticles (ENPs), cerium oxide (nCeO2) and titanium dioxide (nTiO2), directly influenced algal biomass production and algal nutrient accumulation and consequentially indirectly affected overall rice production in simulated rice paddies. Relative to control microcosms, in the presence of fertiliser N, algal biomass production was between 31 and 38% higher in microcosms treated with ENPs. Similarly, the removal of N at the microcosm scale was between 92 and 162% higher in the presence of ENPs, which suggested that ENPs either (1) increased the phytoavailability of fertiliser N or (2) increased algal N-fixation. In the absence of fertiliser N, however, there was no promotion of either algal growth or N accumulation when ENPs were present in microcosms, which suggested that ENPs were influencing the availability and utilisation of fertiliser N rather than increasing the rates of N-mineralisation or algal N-fixation. Although both ENPs had similar effects on algal biomass production and nutrient utilisation, they had very different effects on rice production. When microcosms were amended with nCeO2, algal proliferation was coincident with a 60% reduction in rice growth. However, in contrast, when nTiO2 was added to microcosms, the growth of both algae (62%) and rice (136%) was enhanced. This could be a function of increased N phytoavailability or some other more complex currently unknown interactions between N and nTiO2.

The efficient capture and utilisation of fertiliser nitrogen (N) by cereals has implications for crop growth, grain yield, farm profits, the environment and human nutrition. Extensive research has evaluated many innovative ways to improve the efficiency of fertiliser N recovery (N use efficiency; NUE) by wheat (Triticum aestivum). This review paper, prepared as an outcome of a workshop by the Nutrient Use Efficiency in Wheat Expert Working Group of the Wheat Initiative held in Harpenden, UK in May 2017, is specifically focused on the effects of the co-application of fertiliser N with fertiliser phosphorus (P), potassium (K) and/or sulphur (S) on the efficiencies of capture and utilisation of fertiliser N and its accumulation in wheat grain, as this specific aspect of wheat nutrition was identified by the meeting as a major gap in knowledge. The contribution of P, K and S individually to grain yield has been reasonably well studied, and it is generally assumed that interactions between N and P, K and S will improve crop performance. However, a total of 32 field studies only have been published since 1963 that examine the effects of multiple nutrients on wheat yield and NUE, or changes in the apparent recovery of fertiliser N (% applied) in grain and its impact on grain protein content. The published data showed that NxP, NxK and NxS interactions led to improvements in NUE and the apparent grain recovery of fertiliser N, with the strongest effects generally coming from co-applications of N + P, followed by N + K then N + S treatments. Only five studies explored the combined or interactive effects of NxPxK, and just one considered either NxPxS or NxPxKxS. Grain yields were usually improved by applications of three (N + P + K) or four (N + P + K + S) nutrients in combination, but it was difficult to draw conclusions about effects on fertiliser N recovery and NUE because of the small number of studies, the variability in responses, and the lack of a N fertiliser alone comparative treatment. Grain protein content did not appear to be strongly increased by nutrient interactions, but it did not decrease with higher yields under N, P, K, S fertilisation suggesting that balanced nutrition may provide some protection against protein dilution as yields increase. The available literature suggested that ensuring balanced availability of P, K and S has the potential to reduce the rates of fertiliser N required by wheat because N appears to be accumulated in grain with greater efficiency. This would have both positive agronomic and environmental benefits.

A simple, rapid, colourimetric method for screening biological nitrification inhibitors in plants is presented. Our approach combines the use of the Griess assay to track the rate of nitrite (NO2 −) production by pure cultures of ammonia oxidising bacteria in the presence and absence of nitrification inhibitors with a simple method for collecting root exudates from plants. NO2 − formation was tracked colourimetically on a microplate reader over 9 h of incubation. The advantage of this method is that it provides a simple, high throughput means of measuring biological nitrification inhibition in root exudates, using wild-type bacterial cultures. NO2 − formation rates and inhibition levels measured using the high through-put method were highly correlated with those measured by tracking NO2 − formation using a segmented flow analyser. The method was able to quantify inhibition of Nitrosomonas europaea by the synthetic nitrification inhibitors allythiourea (AT), dicyandiamide (DCD) and 3,4,-dimethylpyrazole phosphate (DMPP) with IC50 values similar to those reported in the literature. The method detected biological nitrification inhibition (BNI) in root exudates from Brachiaria humidicola and the lack of BNI in root exudates from wheat cv. Janz with minimal alteration of the exudates prior to testing. The results also showed that the more common soil ammonia oxidising bacterium (AOB), Nitrosospira multiformis, was much less sensitive to AT and DCD than N. europaea but had similar sensitivity to DMPP. This method provides a potentially useful way of screening large numbers of root exudate samples allowing for phenotyping of the BNI trait in crop and pasture populations which will be required for the trait to be introduced into commercial varieties.

This study investigated whether selenium species in wheat grains could be altered by exposure to different combinations of nitrogen (N) and sulphur (S) fertilisers in an agronomic biofortification experiment. Four Australian wheat cultivars (Mace, Janz, Emu Rock and Magenta) were grown in a glasshouse experiment and exposed to 3 mg Se kg−1 soil as selenate (SeVI). Plants were also exposed to 60 mg N kg−1 soil as urea and 20 mg S kg−1 soil as gypsum in a factorial design (N + S + Se; N + Se; S + Se; Se only). Plants were grown to maturity with grain analysed for total Se concentrations via ICP-MS and Se species determined via HPLC-ICP-MS. Grain Se concentrations ranged from 22 to 70 µg Se g−1 grain (dry mass). Selenomethionine (SeMet), Se-methylselenocystine (MeSeCys), selenohomolanthionine (SeHLan), plus a large concentration of uncharacterised Se species were found in the extracts from grains. SeMet was the major Se species identified accounting for between 9 and 24 µg Se g−1 grain. Exposure to different N and S fertiliser combinations altered the SeMet content of Mace, Janz and Emu Rock grain, but not that of Magenta. MeSeCys and SeHLan were found in far lower concentrations (30 % of total grain Se) in all samples. When N fertiliser was applied (with or without S), the proportion of uncharacterisable Se increased between 60 and 70 % of the total grain Se. The data presented here indicate that it is possible to alter the content of individual Se species in wheat grains via biofortification combined with manipulation of N and S fertiliser regimes. This has potential significance in alleviating or combating both Se deficiency and Se toxicity effects in humans. Refereed/Peer-reviewed

The present study investigated whether the presence or absence of peripubertal ovarian hormones affects sexual preference and conditioned place preference for paced mating in adult female rats primed with 10μg estradiol benzoate and 1mg progesterone. Ovariectomy (OVX) occurred either before or after pubertal development, and 4weeks later rats began a series of behavioral tests. Rats with ovaries removed before the pubertal timeframe (Prepubertal OVX) were more active, more likely to withdrawal from the male compartment, and did not discriminate between mounts and intromissions during paced mating relative to rats with ovaries during puberty (Adult OVX). Both Adult OVX and Prepubertal OVX rats showed a higher preference for the male when hormone primed vs. oil treated and a conditioned place preference for paced mating behavior. The results of the present study demonstrate that some, but not all, aspects of female sexual behavior require ovarian hormones during puberty.

The influence of arsenate and phosphate levels in water on the formation of arsenic-containing lipids (arsenolipids) and water-soluble arsenicals by a unicellular marine alga was investigated by exposing Dunaliella tertiolecta to five regimes of arsenic and phosphate, and determining the biosynthesized organoarsenicals with HPLC/mass spectrometry. Under all conditions, the major arsenolipid produced by D. tertiolecta was the novel phytyl 5-dimethylarsinoyl-2-O-methyl-ribofuranoside (AsSugPhytol546) representing ca. 35-65% of total arsenolipids. The new compound contains a phytol aglycone and a methoxy group replacing a sugar hydroxyl-two structural features not previously observed for arsenolipids. Minor arsenolipids were several previously reported arsenosugar phospholipids (AsSugPLs, in particular AsSugPL958 and the previously unknown AsSugPL978), the relative quantities of which increased with increasing phosphate exposure, and an arsenic-containing hydrocarbon (AsHC360), which remained unaffected by the different treatments. The relative amount of total arsenolipids produced by D. tertiolecta remained remarkably constant (ca. 45% of total As) and independent of the culture conditions. In contrast, with rising As-concentrations we observed an increase of hydrophilic arsenicals, which were dominated by arsenate and arsenosugars. The results highlight a possible major difference in arsenic biochemistry between macroalgae and unicellular algae with potential implications for how various algae handle their natural arsenic exposure in the world's oceans. Refereed/Peer-reviewed

Engineered nanomaterials (ENMs) are increasingly utilised for the remediation of contaminated soils. In this study, contaminant (As, Pb), nutrient (N, P) and trace element (Cu, Fe, Mn, Zn) phytoavailability in three Australian soils contaminated (b10 years) with As (≈100 mg As kg−1 soil) or Pb (≈300 mg Pb kg−1 soil) was determined periodically. These soils were exposed to two ENMs (cerium dioxide – nCeO2 or titanium dioxide –nTiO2) (applied to soil at a concentration of 500mgENMkg−1 soil) with contaminant, nutrient and trace elementphy to availability assessed over a 260-day period. While As phytoavailability was not influenced by either ENM,the presence of nCeO2 in some soils increased Pb phytoavailability approximately two fold at the conclusion ofthe experiment (day 260), which was attributed to nCeO2 decreasing soil pH and/or outcompeting Pb2+ ionsfor sorption sites.More significantly, both ENMs significantly altered the phytoavailability of N, P and Zn across soils. In some instancesN90% of the soil N was lost in the presence of both ENMs, while in some instances the phytoavailability of P and Zn was tripled and doubled respectively in the presence of ENMs.For N it was hypothesised that both ENMs altered the mineralisation of organic N and/or soil nitrification rates due to the catalytic and/or anti-microbial properties of the ENMs. For P, it was hypothesised that antimicrobial effects of both ENMs altered the activity of P-solubilising microbes. For Zn competition between the positively charged ENMs and Zn2+ ions was the most likely mechanism for altered Zn phytoavailability. This study suggested that while ENMs can potentially be effective as metal remediation agents when applied to soils, there are however a range of potentially deleterious ‘non-target’ effects on soil ecosystems that have not as yet been widely considered. Refereed/Peer-reviewed

Nitrification inhibitors (NIs) such as 3,4,-dimethylpyrazole phosphate (DMPP), are used to suppress the abundance of ammonia-oxidising micro-organisms responsible for nitrification. In agriculture, NIs are used to retain soil mineral nitrogen (N) as ammonium to minimise the risk of losses of N from agricultural soils. It is currently unclear whether DMPP-induced nitrification inhibition can prevent losses of N from the light soils prevalent across the main rain-fed cropping regions of Western Australia, or whether it can improve the productivity or N uptake by broadacre crops such as wheat. Herein, we report on a series of glasshouse and field studies that examined the effect of applications of DMPP in conjunction with urea (as ENTEC urea; Incitec Pivot, Melbourne, Vic., Australia) on: (1) soil nitrification rates; (2) the abundance of ammonia-oxidising bacteria and archaea (AOB and AOA respectively); and (3) wheat performance (grain yield, protein content and N accumulation). A glasshouse study demonstrated that DMPP inhibited nitrification (for up to ∼40 days after application) and reduced the abundance of AOB (by 50%), but had no effect on AOA abundance, wheat grain yield or protein content at any fertiliser N rate. Across six field experiments, DMPP also limited nitrification rates and reduced AOB abundance for approximately the first 40 days after application. However, by the end of the growing season, DMPP use had not increased soil mineral N resources or impaired AOB abundance compared with urea-only applications. In addition, DMPP had no effect on AOA abundance in any trial and did not improve crop performance in most trials. Refereed/Peer-reviewed

The effectiveness of the nitrification inhibitor 3,4,-dimethylpyrazole phosphate (DMPP) on sandy soils containing low nitrifying microbial abundance has not been established. Two coarse-grained soils, representative of Western Australia's agricultural zones, were incubated with 100mgNkg-1 soil, added as either urea, urea+DMPP or urea+nitrapyrin as an alternative nitrification inhibitor for comparative purposes. Ammonium (NH4+) and nitrate (NO3-) concentrations, potential nitrification rates (PNR) and the abundance of ammonia-oxidising bacteria (AOB) and archaea (AOA) were measured over time. Interactions between soil type and inhibitor type altered the extent of nitrification observed in these soils. When N was supplied as urea alone, NH4+-N concentrations decreased from 100mgNkg-1 soil to approximately 20mgNkg-1 soil in the high nutrient soil (Williams) and approximately 60mgNkg-1 soil in the low nutrient soil (Vasse). These differences were reflected in AOB abundance, which was higher (∼105genecopiesg-1 soil) in Williams soil than in Vasse soil (

Hydrothermal vents are surficial expressions of subsurface geological and hydrological processes. Fluids emitting from active vents are chemically distinct from bottom seawater, and are enriched in dissolved metals and metalloids, including arsenic. Vent organisms accumulate arsenic but the arsenic speciation in these non-photosynthetic organisms is largely unknown. Here, arsenic concentrations and chemical species were measured in three deep sea hydrothermal vent worms (Ridgeia piscesae, Paralvinella sulfincola and Paralvinella palmiformis ) from the Juan de Fuca Ridge in the Northwest pacific. R. piscesae has similar arsenic concentrations (3.8–35 µg g−1) to shallow water polychaetes while P. sulfincola and P. palmiformis have significantly higher arsenic concentrations (420–1417 and 125–321 µg g−1 respectively). R. piscesae contains appreciable quantities of inorganic arsenic (36±14%), monomethyl arsenic (2±2%), dimethyl arsenic (34±21%), an unknown methyl arsenical (7±16%), OSO3-arsenosugar (5±9%), TETRA (4±5%), ThioPO4/ThioDMAE (1±2%) and an unknown thio-arsenical (12±14%). These results suggests that host and symbionts are either involved in the methylation of arsenic, or are bathed in fluids enriched in methylated arsenic as a result of free-living microbial activity. The host carrying out methylation, however, cannot be ruled out. In contrast, 96–97% of the arsenic in P. sulfincola and P. palmiformis is inorganic arsenic, likely the result of arsenic precipitation within and upon the mucus they ingest while feeding. While all worms have oxo- and thio arsenosugars (2–30%), Paralvinella also have small amounts of arsenobetaine (

The effects of inorganic arsenic on plants, the mechanisms involved in the uptake and transport of arsenic and how inorganic arsenic enters food chains are well documented. Regulatory limits have been established to control the inorganic arsenic concentrations in certain foods including rice. There is, however, a knowledge gap with respect to dimethylarsenic concentrations. In this study rice was grown hydroponically and exposed to varying DMA concentrations. High levels of DMA were detrimental to rice plants whereby plants showed symptoms consistent with Straighthead disease, a disease that results in dramatic yield losses. Refereed/Peer-reviewed

Environmental context Knowledge of the pathways by which arsenic is accumulated and transferred in marine ecosystems is scarce. Molluscs are important keystone organisms providing a link between primary producers (micro and macroalgae) and higher trophic levels such as fish. The present study examines the accumulation and species of arsenic in common bivalve molluscs from south-east Australia to understand the cycling of arsenic in marine food webs. Abstract The present paper reports the whole-tissue total arsenic concentrations and water-soluble arsenic species in 12 common coastal Australian bivalve mollusc species. Mean arsenic concentrations ranged from 18 to 57 g g -1 dry mass. Planktivores had significantly less arsenic (20-40 g g -1; 22 ± 3 g g -1) than did suspension and deposit feeders (36-57 g g -1; 43 ± 7 g g -1), with those associated with fine clay-silt sediments (49 ± 7 g g -1) having significantly more arsenic than those associated with sand substrates (31 ± 11 g g -1). Most planktivores and suspension feeders had similar arsenic species, with high proportions of arsenobetaine (AB) (64-92 %) and relatively low proportions of other arsenic species (0.55-15.8 %). Lower proportions of AB (13-57 %) and larger proportions of inorganic arsenic (6-7 %) were found in deposit feeders, reflecting increased exposure to inorganic arsenic in sediments. The study indicated that at lower trophic levels, organisms feed on algae and suspended matter containing a range of arsenic species including arsenosugars and AB. The implications for arsenic cycling are that as all bivalve molluscs accumulate AB and are a source of AB in benthic food webs. Because all bivalve molluscs also contained appreciable concentrations of arsenoriboses, precursors are present for the de novo synthesis of AB. As well, deposit feeders have higher proportions of inorganic arsenic that can be metabolised to different end products when ingested by higher trophic organisms Refereed/Peer-reviewed

The contamination of cereals with arsenic (As) is a global health and agronomic concern. This study compared the physiological response, As uptake and As speciation in the grains and above ground tissues of 20 wheat cultivars exposed to 5 mg As kg −1 soil as either arsenate (As V ) or dimethylarsenate (DMA) under glasshouse conditions. Germination rates for the majority of cultivars exceeded 80% for the majority of cultivars when exposed to As V , but fell significantly to 20–40% when exposed to DMA. For a number of cultivars, grain yields were 20–50% lower when plants were exposed to DMA compared to As V . Grain As concentrations were between 0.6 an d 1.6 μg As g −1 grain across the twenty cultivars when exposed to As V , whereas grain As concentrations were much higher (2.2–4.6 μg As g −1 grain) when exposed to DMA. When plants were exposed to As V , 100% of the As present in the grain was found as inorganic As while in plants exposed to DMA, 70–90% of As was present as DMA with the remainder found as inorganic As. DMA is believed to be incorporated by plants via silica (Si) acid channels and assessment of grain Si concentrations demonstrated that up to 40% less Si was accumulated in grains when plants were exposed to DMA. The decreased germination rates and grain yields in the presence of DMA is similar to the symptoms described for straight head disease in rice, which has been linked to DMA exposure. The results presented here indicate some analogous processes occur in wheat to those described in rice. We hypothesise that exposure to DMA may have inhibited Si-metabolism and translocation which resulted in both developmental impairment and possibly an increased susceptibility to soil pathogens. Refereed/Peer-reviewed

Eight wheat cultivars were grown in soil amended with arsenate (AsV) at a concentration of 15 mg As kg−1 soil, with or without a triple super phosphate amendment of 40 mg P kg−1 soil. All eight wheat cultivars accumulated higher As in stems/leaves (9–23 μg As g−1) and chaff (9–22 μg As g−1) compared with the grain (0.6–1.6 μg As g−1). The As present in stems/leaves, grain and chaff was found as inorganic As species—AsV or arsenite (AsIII). For most cultivars, increased P availability had minimal influence on As accumulation in chaff tissues. If this data is reflective of what occurs in situ, then As can accumulate in chaff at similar concentrations to stem and leaf tissues which are much higher than in grain. Further research is required to determine the risks of As accumulation in livestock products (meat and dairy) when fed with As-contaminated wheat chaff. Refereed/Peer-reviewed

This study investigated whether applying dicyandiamide (DCD) and guanyl thiourea (GTU) in conjunction with urea improves the efficacy of nitrification inhibition relative to traditional fertiliser application of urea or urea + DCD. Urea at a rate of 100 mg N kg(-1) soil was applied to soil microcosms (high nutrient tenosol and low nutrient hydrosol) which were treated with either no inhibitor (urea-only); 15 mg DCD kg(-1) soil or 15 mg DCD kg(-1) soil plus 21 mg GTU kg soil(-1). Mineral N (NH4+ & NO3-) concentrations, potential nitrification rates (PNR) and abundances of ammonia oxidising bacteria (AOB) were measured over time. After 100-days incubation, similar to 73 mg N kg(-1) soil was found as NH4+ when urea + DCD + GTU were applied to the tenosol. NH4+ concentrations were lower (11-32 mg N kg(-1) soil) when urea or urea + DCD were applied. This suggests that the application of GTU in conjunction with DCD elongated the effects of nitrification inhibition. In both soils, PNRs were faster and AOB abundances (gene copies g(-1) soil) were higher when urea was applied without nitrification inhibitors. There were, however, no differences in PNR or AOB abundances in either soil type when 'urea + DCD' or 'urea + DCD + GTU' were applied. The results indicate that the application of GTU with DCD may extend nitrification inhibition in certain soil types. This finding has the potential to improve the efficacy of commercially available and widely used inhibitors such as DCD. Refereed/Peer-reviewed

Deprivation or fragmentation of sleep for longer than 2days significantly inhibits cell proliferation and neurogenesis in the hippocampus of adult rats and mice. Signaling pathways that mediate these effects have yet to be clarified. Although deprivation procedures can stimulate adrenal corticosterone (CORT) release, suppression of cell proliferation by sleep deprivation does not require elevated CORT. We examined a role for interleukin-1β (IL-1β), a pro-inflammatory cytokine that is increased by sleep loss and that mediates effects of stress on hippocampal neurogenesis. Wild type (WT) and IL-1 receptor 1 knockout (IL1RI-KO) mice were subjected to rapid-eye-movement sleep deprivation (RSD) for 72-h using the multiple platform-over-water method. Mice were administered BrdU (100mg/kg) i.p. at hour 70 of RSD and were sacrificed 2-h later. New cells were identified by immunoreactivity (ir) for BrdU and Ki67 in the granular cell layer/subgranular zone (GCL/SGZ) and the hilus. In Experiment 1, WT and IL1RI-KO mice, by contrast with respective control groups, exhibited significantly fewer BrdU-ir and Ki67-ir cells. In Experiment 2, WT and IL1RI-KO mice were adrenalectomized (ADX) and maintained on constant low-dose CORT by osmotic minipumps. RSD reduced cell proliferation by 32% (p0.01) in ADX-WT animals but did not significantly reduce proliferation in ADX IL1RI-KO animals (p0.1). These results imply that RSD suppresses cell proliferation by the presence of wake-dependent factors (either elevated CORT or IL-1β signaling are sufficient), rather than the absence of a REM sleep-dependent process. The generality of these findings to other sleep deprivation methods and durations remains to be established.

Environmental context In marine environments, inorganic arsenic present in seawater is transformed to organoarsenic species, mainly arsenoribosides in algae and arsenobetaine in animals. These transformations decrease the toxicity of arsenic, yet the fate of arsenoribosides and arsenobetaine when marine organisms decompose is unknown. We review the current literature on the degradation of these organoarsenic species in marine systems detailing the drivers behind their degradation, and also discuss the environmental relevance of laboratory-based experiments. Abstract Despite arsenoribosides and arsenobetaine (AB) being the major arsenic species in marine macro-algae and animals they have never been detected in seawater. In all studies reviewed arsenoribosides from marine macro-algae were degraded to thio-arsenoribosides, dimethylarsinoylethanol (DMAE), dimethylarsenate (DMA), methylarsenate (MA) with arsenate (AsV) the final product of degradation. The use of different macro-algae species and different experimental microcosms did not influence the arsenoriboside degradation pathway. The use of different experimental approaches, however, did influence the rate and extent at which arsenoriboside degradation occurred. This was almost certainly a function of the complexity of the microbial community within the microcosm, with greater complexity resulting in rapid and more complete arsenoriboside degradation. AB from decomposing animal tissues is degraded to trimethylarsine oxide (TMAO) or dimethylarsenoacetate (DMAA), DMA and finally AsV. The degradation of AB unlike arsenoribosides occurs via a dual pathway with environmental or microbial community variability influencing the pathway taken. The environmental validity of different experimental approaches used to examine the fate of organoarsenic species was also reviewed. It was evident that although liquid culture incubation studies are cheap and reproducible they lack the ability to culture representative microbial communities. Microcosm studies that include sand and sediment are more environmentally representative as they are a better simulation of marine ecosystems and are also likely to facilitate complex microbial communities. An added benefit of microcosm studies is that they are able to be run in parallel with field-based research to provide a holistic assessment of the degradation of organoarsenic species in marine environments. Refereed/Peer-reviewed

This review investigates the arsenic species produced by and found in marine unicellular algae to determine if unicellular algae contribute to the formation of arsenobetaine (AB) in higher marine organisms. A wide variety of arsenic species have been found in marine unicellular algae including inorganic species (mainly arsenate-As(V)), methylated species (mainly dimethylarsenate (DMA)), arsenoribosides (glycerol, phosphate, and sulfate) and metabolites (dimethylarsenoethanol (DMAE)). Subtle differences in arsenic species distributions exist between chlorophyte and heterokontophyte species with As(V) commonly found in water-soluble cell fractions of chlorophyte species, while DMA is more common in heterokontophyte species. Additionally, different arsenoriboside species are found in each phyla with glycerol and phosphate arsenoribosides produced by chlorophytes, whereas glycerol, phosphate, and sulfate arsenoribosides are produced by heterokontophytes, which is similar to existing data for marine macro-algae. Although arsenoribosides are the major arsenic species in many marine unicellular algal species, AB has not been detected in unicellular algae which supports the hypothesis that AB is formed in marine animals via the ingestion and further metabolism of arsenoribosides. The observation of significant DMAE concentrations in some unicellular algal cultures suggests that unicellular algae-based detritus contains arsenic species that can be further metabolized to form AB in higher marine organisms. Future research establishing how environmental variability influences the production of arsenic species by marine unicellular algae and what effect this has on arsenic cycling within marine food webs is essential to clarify the role of these organisms in marine arsenic cycling. Refereed/Peer-reviewed

Arsenoribosides (as glycerol; phosphate; sulfate and sulfonate) persisted in all bacteria-inoculated cultures irrespective of the source of bacteria (seawater, macro-algae surface) or the culture media used (DIFCO Marine Broth 2216 or novel blended Hormosira banksii tissue-based). This is unlike observations from traditional macro-algae tissue decomposition studies or in nature. In addition known arsenoriboside degradation products such as dimethylarsenoethanol (DMAE), dimethylarsenate (DMA), methylarsenate (MA) and arsenate - As(V) were not detected in any cultures. Consequently, the use of bacterial culture incubation experiments to explain the fate of arsenoribosides in marine systems appears limited as the processes governing arsenoriboside degradation in these experiments appear to be different to those in macro-algae tissue decomposition studies or in nature. Refereed/Peer-reviewed

To assess whether bacteria influence the biogeochemical cycling of arsenic by laboratory cultures of the marine phytoplankton Dunaliella tertiolecta, the arsenic species produced by D. tertiolecta were compared in “operationally sterile” and bacteria spiked cultures. It was observed that glycerol (Gly-) arsenoriboside (41–78%), phosphate (PO 4 −) arsenoriboside (7–38%) and arsenate (As(V)) (15–21%) were the major water-soluble arsenic species in all D. tertiolecta cultures irrespective of whether cultures were operationally sterile or contained added bacteria. PO 4 -riboside (46–74%) and Gly-riboside (24–36%) were also the major arsenic species in hydrolysed lipid extracts of D. tertiolecta irrespective of whether cultures were operationally sterile or contained bacteria. In addition to similarities in the arsenic species produced, total arsenic concentrations and culture growth did not differ relative to whether cultures were operationally sterile or not. Similar bacterial strains were identified in all D. tertiolecta cultures irrespective of whether bacteria were added or not. Consequently, it is evident that the presence of “foreign” or “added” bacteria in D. tertiolecta has minimal influence on the metabolism and cycling of arsenic by phytoplankton. Thus, the use of laboratory phytoplankton cultures containing bacteria may be appropriate means to investigate arsenic biogeochemical cycling unlike previously believed. Refereed/Peer-reviewed

To investigate the release and degradation of arsenoribosides associated with the brown alga Ecklonia radiata, tissues were collected in various marine micro-habitats (water column, sand intertidal, and rock platform intertidal) to establish the importance of decomposition stage and the micro-habitat in which decomposition occurs on arsenoriboside degradation. Total arsenic concentrations in E. radiata tissues varied in a similar pattern across all three sampling locations (Lake Tabourie, Burrill Lake, and Ulladulla Harbour) with concentrations in live tissues (53–124 μg As g −1 (dry mass)) greater than concentrations in tissues decomposing in the water column (28–90 μg As g −1 (dry mass)), which were in turn higher than concentrations in tissues decomposing in intertidal environments (16–21 μg As g −1 (dry mass)). Arsenoribosides, specifically sulfonate (SO 3 -), phosphate (PO 4 -), and glycerol (Gly-) accounted for all of the arsenic extracted from live E. radiata tissues. Arsenoribosides also accounted for 100 % of the extractable arsenic species in E. radiata tissues decomposing in the water column. The proportions of arsenic species in decomposing E. radiata tissue from intertidal environments varied with sampling location and therefore micro-habitat. In rock platform-based intertidal zones (Burrill Lake and Ulladulla harbour), considerable concentrations of unextractable arsenic (10–60 %) were present plus known arsenoriboside degradation products such as dimethylarsinoylethanol (DMAE), dimethylarsenate (DMA), and arsenate (As(V)). In sand/beach-based intertidal zones, however, the vast majority of arsenic (≈95 %) was unextractable with only small concentrations of arsenoribosides and As(V) present. This study demonstrates that the release and further degradation of arsenoribosides from E. radiata tissues occurs in a two-step process with arsenoribosides released via leaching, whilst E. radiata remains suspended within the water column. Arsenoribosides are then degraded to various intermediate arsenic species once E. radiata tissues settle on intertidal environments; however, the degree of degradation varies relative to whether decomposition occurs on rock platform or sand-based environments. These results illustrate the key role of marine micro-habitats in the degradation of arsenoribosides contained within marine macro-algae. Refereed/Peer-reviewed

© 2015 Springer International Publishing Switzerland. Chemical methods have been used for the remediation of arsenic (As)-contaminated water; however, ecological consequences of these methods have not been properly addressed. The present study evaluated the effects of the Fe-oxide-coated sand (IOCS) remediation method on As toxicity to freshwater organisms (Lemna disperma, Chlorella sp. CE-35, and Ceriodaphnia cf. dubia). The As removal efficiency by IOCS decreased substantially with time. The IOCS remediation method was less effective at suppressing the toxicity of AsV than AsIII to L. disperma but was highly effective in reducing both the AsIII and AsV toxicity to C. cf. dubia. The growth of Chlorella sp. was significantly higher (p < 0.05) in remediated and pre-remediated water than in controls (non-As-contaminated filtered Colo River water) for AsIII, while the opposite was observed for AsV, indicating that AsV is more toxic than AsIII to this microalga. Although the IOCS can efficiently remove As from contaminated water, residual As and other constituents (e.g. Fe, nitrate) in the remediated water had a significant effect on freshwater organisms.

The accumulation, subcellular distribution and speciation of arsenic in the polychaete Arenicola marina were investigated under different laboratory exposure conditions representing a range of metal bioavailabilities, to gain an insight into the physiological mechanisms of how A. marina handles bioaccumulated arsenic and to improve our understanding of the potential ecotoxicological significance of bioaccumulated arsenic in this deposit-feeder. The exposure conditions included exposure to sublethal concentrations of dissolved arsenate, exposure to sublethal concentrations of sediment-bound metal mining mixtures, and exposure to lethal concentrations of sediment-bound metal mining mixtures and arsenic- and multiple metalspiked sediments. The sub-lethal exposures indicate that arsenic bioaccumulated by the deposit-feeding polychaete A. marina is stored in the cytosol as heat stable proteins (∼50%) including metallothioneins, possibly as As (III)- thiol complexes. The remaining arsenic is mainly accumulated in the fraction containing cellular debris (∼20%), with decreasing proportions accumulated in the metal-rich granules, organelles and heat-sensitive proteins fractions. A biological detoxified metal compartment including heat stable proteins and the fraction containing metal-rich granules is capable of binding arsenic coming into the cells at a constant rate under sublethal arsenic bioavailabilities. The remaining arsenic entering the cell is bound loosely into the cellular debris fraction, which can be subsequently released and diverted to an expanding detoxified pool. Our results suggest that a metal sensitive compartment comprising the cellular debris, enzymes and organelles fractions may be more representative of the toxic effects observed. Refereed/Peer-reviewed

Axenic cultures of the phytoplankton Dunaliella tertiolecta were dosed with either arsenate [As(V)], methylarsonate (MA) or arsenobetaine (AB) at environmentally realistic concentrations (2 μg l-1) to investigate incorporation and transformation of arsenic species. Total arsenic concentrations in cultures dosed with As(V) were significantly higher than those dosed with MA and AB (6–10 μg g-1 compared to 1–3 μg g-1). Arsenic concentrations in As(V)-dosed cultures increased over time, whereas arsenic concentrations in MA- and AB-dosed cultures remained constant, indicating that As(V) is rapidly and continuously incorporated into the cell in comparison to MA and AB. Arsenic was found predominantly in the residue fractions (29–55%) of all cultures, irrespective of culture age. This was attributed to the ability of inorganic arsenic as arsenite [As(III)] to bind to proteins and/or phytochelatins. 2-Dimethylarsinoylethanol (DMAE) was the main arsenic species found in lipid cell fractions. Within the water-soluble and residue cell fractions, arsenic was isolated primarily as As(V), although it is likely the extraction procedure may have converted some As(III) to As(V). Small amounts of As(III), MA, dimethylarsinate (DMA) and arsenoribosides were also found in the lipid and water soluble As fractions. All cultures showed an increase in DMA and arsenoriboside species over time. The significance of these results is that while AB, the major arsenical in marine animals, is not produced or accumulated by this phytoplankton species, the possible precursors to AB formation are produced.

Environmental contextIn countries where inhabitants are not exposed to arsenic-contaminated drinking water, food is the major source of potentially toxic inorganic arsenic. To complement the existing worldwide dataset on arsenic in rice, data are presented on Australian- and overseas-grown rice, and assessed in terms of possible risk. Only a diet comprising multiple serves of some rice products per day poses a potential risk to young children. AbstractArsenic concentrations and speciation measurements were determined for six varieties of Australian-grown rice (n = 130), imported rice (n = 53) and rice products (n = 56) from supermarkets. Total As, inorganic As and dimethylarsinic acid (DMA) concentrations in Australian rice ranged from 16 to 630 µg As kg−1 (mean ± s.d.: 220 ± 122 µg kg−1), 16 to 250 µg As kg−1 (92 ± 52 µg As kg−1) and

The influence of As(V) (50 μg L − 1 & 2 μg L − 1 ) and PO 4 3 − (3 mg L − 1 & 0.12 mg L − 1 ) exposures on arsenic cycling by the marine phytoplankton Dunaliella tertiolecta was investigated both separately and in combination. Total arsenic concentrations in D. tertiolecta tissue ranged from 8 to 10 μg g − 1 when exposed to 50 μg L − 1 As(V), and 2–4 μg g − 1 when exposed to 2 μg L − 1 As(V), with PO 4 3 − exposure having little to no influence on total arsenic concentrations. Arsenic was evenly distributed (≈ 33%) between the three major biochemical cell fractions (lipid, water, residue) in cultures exposed to high As(V):high PO 4 3 − concentrations. Under low As(V):high PO 4 3 − exposures arsenic was predominantly lipid-soluble (40–55%) and residue bound (30–40%). When exposed to high As(V):low PO 4 3 − concentrations arsenic was predominantly residue bound (50–70%) and lipid-soluble (20–40%), whilst under low As(V):low PO 4 3 − exposures arsenic was predominantly residue bound (75–80%). As(V) was the dominant arsenic species present in the water-soluble cell fractions of all D. tertiolecta cultures. Under high PO 4 3 − concentrations As(V) accounted for greater than 93% of the extractable water-soluble arsenic, with As(III) the only other species detected. Conversely, under low PO 4 3 − concentrations As(V) accounted for between 66 and 71% of the extractable arsenic with As(III) (16–26%) and PO 4 -riboside (8–13%) present. Under high As(V):high PO 4 3 − concentrations As(V) was the major arsenic species in hydrolysed lipid extracts accounting for approximately 56% of the extractable arsenic, with Gly-riboside (26%), PO 4 -riboside (13%) and As(III) (5%) also present. Under low As(V):high PO 4 3 − conditions As(V) only accounted for approximately 18% of the extractable arsenic with Gly-riboside (44%) and PO 4 -riboside (38%) more prominent. Under low PO 4 3 − conditions Gly-riboside was the major arsenic species (84–92%) irrespective of As(V) exposure with As(V) (8–10%) and PO 4 -riboside (6%) also present. This study demonstrates that D. tertiolecta alters its arsenic and nutrient cycling processes depending on the chemical composition of the culture media or surrounding environment. Future research should endeavour to culture laboratory phytoplankton at nutrient and arsenic concentrations that mimic the natural environment to ensure that observations generated in laboratory experiments can be used to describe arsenic cycling in marine systems.

Circadian clocks in many brain regions and peripheral tissues are entrained by the daily rhythm of food intake. Clocks in one or more of these locations generate a daily rhythm of locomotor activity that anticipates a regular mealtime. Rats and mice can also anticipate two daily meals. Whether this involves 1 or 2 circadian clocks is unknown. To gain insight into how the circadian system adjusts to 2 daily mealtimes, male rats in a 12∶12 light-dark cycle were fed a 2 h meal either 4 h after lights-on or 4 h after lights-off, or a 1 h meal at both times. After 30 days, brain, blood, adrenal and stomach tissue were collected at 6 time points. Multiple clock genes from adrenals and stomachs were assayed by RT-PCR. Blood was assayed for corticosterone and ghrelin. Bmal1 expression was quantified in 14 brain regions by in situ hybridization. Clock gene rhythms in adrenal and stomach from day-fed rats oscillated in antiphase with the rhythms in night-fed rats, and at an intermediate phase in rats fed twice daily. Corticosterone and ghrelin in 1-meal rats peaked at or prior to the expected mealtime. In 2-meal rats, corticosterone peaked only prior the nighttime meal, while ghrelin peaked prior to the daytime meal and then remained elevated. The olfactory bulb, nucleus accumbens, dorsal striatum, cerebellum and arcuate nucleus exhibited significant daily rhythms of Bmal1 in the night-fed groups that were approximately in antiphase in the day-fed groups, and at intermediate levels (arrhythmic) in rats anticipating 2 daily meals. The dissociations between anticipatory activity and the peripheral clocks and hormones in rats anticipating 2 daily meals argue against a role for these signals in the timing of behavioral rhythms. The absence of rhythmicity at the tissue level in brain regions from rats anticipating 2 daily meals support behavioral evidence that circadian clock cells in these tissues may reorganize into two populations coupled to different meals.

In the environment, arsenic (As) exists in a number of chemical species, and arsenite (As(III)) and arsenate (As(V)) dominate in freshwater systems. Toxicity of As species to aquatic organisms is complicated by their interaction with chemicals in water such as phosphate that can influence the bioavailability and uptake of As(V). In the present study, the toxicities of As(III), As(V) and dimethylarsinic acid (DMA) to three freshwater organisms representing three phylogenetic groups: a phytoplankton (Chlorella sp. strain CE-35), a floating macrophyte (Lemna disperma) and a cladoceran grazer (Ceriodaphnia cf. dubia), were determined using acute and growth inhibition bioassays (EC₅₀) at a range of total phosphate (TP) concentrations in OECD medium. The EC₅₀ values of As(III), As(V) and DMA were 27 ± 10, 1.15 ± 0.04 and 19 ± 3 mg L(-1) for Chlorella sp. CE-35; 0.57 ± 0.16, 2.3 ± 0.2 and 56 ± 15 mg L(-1) for L. disperma, and 1.58 ± 0.05, 1.72 ± 0.01 and 5.9 ± 0.1 mg L(-1) for C. cf. dubia, respectively. The results showed that As(III) was more toxic than As(V) to L. disperma; however, As(V) was more toxic than As(III) to Chlorella sp. CE-35. The toxicities of As(III) and As(V) to C. cf. dubia were statistically similar (p>0.05). DMA was less toxic than iAs species to L. disperma and C. cf. dubia, but more toxic than As(III) to Chlorella sp. CE-35. The toxicity of As(V) to Chlorella sp. CE-35 and L. disperma decreased with increasing TP concentrations in the growth medium. Phosphate concentrations did not influence the toxicity of As(III) to either organism. Chlorella sp. CE-35 showed the ability to reduce As(V) to As(III), indicating a substantial influence of phytoplankton on As biogeochemistry in freshwater aquatic systems.

A variety of observations from several rodent species suggest that a serotonin (5-HT) input to the suprachiasmatic nucleus (SCN) circadian pacemaker may play a role in resetting or entrainment of circadian rhythms by non-photic stimuli such as scheduled wheel running. If 5-HT activity within the SCN is necessary for activity-induced phase shifting, then it should be possible to block or attenuate these phase shifts by reducing 5-HT release or by blocking post-synaptic 5-HT receptors. Animals received one of four serotonergic drugs and were then locked in a novel wheel for 3 h during the mid-rest phase, when novelty-induced activity produces maximal phase advance shifts. Drugs tested at several doses were metergoline (5-HT1/2 antagonist; i.p.), (+)-WAY100135 (5-HT1A postsynaptic antagonist, which may also reduce 5-HT release by an agonist effect at 5-HT1A raphe autoreceptors; i.p.), NAN-190 (5-HT1A postsynaptic antagonist, which also reduces 5-HT release via an agonist effect at 5-HT1A raphe autoreceptors; i.p.) and ritanserin (5-HT2/7 antagonist; i.p. and i.c.v.). Mean and maximal phase shifts to running in novel wheels were not significantly affected by any drug at any dose. These results do not support a hypothesis that 5-HT release or activity at 5HT1, 2 and 7 receptors in the SCN is necessary for the production of activity-induced phase shifts in hamsters.

Recently two new classes of arsenic species have been identified, thio-methylated arsenic species in marine organisms where the oxygen bonded to arsenic is replaced by an S group and thioarsenate species in sulfide rich water environments. Here we describe the use of HPLC-ICPMS to measure thio arsenic species found in marine biota and a geothermal water sample from a sulfide rich environment. Thio-methylated arsenic species were separated using an Alantis C18 reverse phase column and elution with an aqueous 20. mM phosphate buffer (pH3). Thioarsenate species were separated using an Ion Pac, AS16 anion exchange column with a sodium hydroxide gradient (20-100. mM) and the use of an anionic self-regenerating suppressor to remove sodium ions before the ICPMS spray chamber. Thio-methylated arsenic species in marine biota are stable to freeze drying and microwave extraction with methanol-water (1:1. v/v) at 70. °C. Rotational mixing at 25. °C for long periods causes the loss of species. Freeze-thawing of extracts results in oxidation of species. Thio-methylated arsenic species in extracts are stable if the solvent is removed and the residues stored dry in a dessicator. Thioarsenate species in water samples are stable during analysis if manipulated under a nitrogen atmosphere and if during chromatography mobile phases are degassed and precautions taken to exclude air from samples. Refereed/Peer-reviewed

Environmental context Arsenoribosides are the major arsenic species in marine macro-algae, yet inorganic arsenic is the major arsenic species found in seawater. We investigated the degradation of arsenoribosides associated with Ecklonia radiata by the use of microcosms containing both natural and autoclaved seawater and sand. The decomposition and persistence of arsenic species was linked to the use of autoclaved seawater and sand, which suggests that arsenoriboside degradation is governed by the microbial composition of microenvironments within marine systems. Abstract We investigated the influence of microbial communities on the degradation of arsenoribosides from E. radiata tissues decomposing in sand and seawater-based microcosms. During the first 30 days, arsenic was released from decomposing E. radiata tissues into seawater and sand porewaters in all microcosms. In microcosms containing autoclaved seawater and autoclaved sand, arsenic was shown to persist in soluble forms at concentrations (9-18μg per microcosm) far higher than those present initially (∼3μg per microcosm). Arsenoribosides were lost from decomposing E. radiata tissues in all microcosms with previously established arsenoriboside degradation products, such as thio-arsenic species, dimethylarsinoylethanol (DMAE), dimethylarsenate (DMA) and arsenate (AsV) observed in all microcosms. DMAE and DMA persisted in the seawater and sand porewaters of microcosms containing autoclaved seawater and autoclaved sand. This suggests that the degradation step from arsenoribosides DMAE occurs on algal surfaces, whereas the step from DMAE AsV occurs predominantly in the water-column or sand-sediments. This study also demonstrates that disruptions to microbial connectivity (defined as the ability of microbes to recolonise vacant habitats) result in alterations to arsenic cycling. Thus, the re-cycling of arsenoribosides released from marine macro-algae is driven by microbial complexity plus microbial connectivity rather than species diversity as such, as previously assumed. © CSIRO 2014. Refereed/Peer-reviewed

Environmental contextAlthough arsenic occurs at high concentrations in many marine systems, the influencing factors are poorly understood. The arsenic content of sediments, detritus, suspended particles and organisms have been investigated from different trophic levels in an open seagrass ecosystem. Total arsenic concentrations and arsenic species were organism-specific and determined by a variety of factors including exposure, diet and the organism physiology. AbstractThe distribution and speciation of arsenic within an open marine seagrass ecosystem in Lake Macquarie, NSW, Australia is described. Twenty-six estuarine species were collected from five trophic groups (autotrophs, suspension-feeders, herbivores, detritivores and omnivores, and carnivores). Sediment, detritus, epibiota and micro-invertebrates were also collected and were classified as arsenic source samples. There were no significant differences in arsenic concentrations between trophic groups and between pelagic and benthic feeders. Benthic-dwelling species generally contained higher arsenic concentrations than pelagic-dwelling species. Sediments, seagrass blades and detritus contained mostly inorganic arsenic (50–90 %) and arsenoribosides (10–26 %), with some methylarsonate (9.4–14.6 %) and dimethyarsinate (7.9–9.7 %) in seagrass blades and detritus. Macroalgae contained mostly arsenoribosides (40–100 %). Epibiota and other animals contained predominately arsenobetaine (63–100 %) and varying amounts of dimethyarsinate (0–26 %), monomethyarsonate (0–14.6 %), inorganic arsenic (0–2 %), trimethylarsenic oxide (0–6.6 %), arsenocholine (0–12 %) and tetramethylarsonium ion (0–4.5 %). It was concluded that arsenic concentrations and species within the organisms of the Lake Macquarie ecosystem are species-specific and determined by a variety of factors including exposure, diet and the physiology of the organisms.

The dorsomedial hypothalamus (DMH) is a site of circadian clock gene and immediate early gene expression inducible by daytime restricted feeding schedules that entrain food anticipatory circadian rhythms in rats and mice. The role of the DMH in the expression of anticipatory rhythms has been evaluated using different lesion methods. Partial lesions created with the neurotoxin ibotenic acid (IBO) have been reported to attenuate food anticipatory rhythms, while complete lesions made with radiofrequency current leave anticipatory rhythms largely intact. We tested a hypothesis that the DMH and fibers of passage spared by IBO lesions play a time-of-day dependent role in the expression of food anticipatory rhythms. Rats received intra-DMH microinjections of IBO and activity and body temperature (T(b)) rhythms were recorded by telemetry during ad-lib food access, total food deprivation and scheduled feeding, with food provided for 4-h/day for 20 days in the middle of the light period and then for 20 days late in the dark period. During ad-lib food access, rats with DMH lesions exhibited a lower amplitude and mean level of light-dark entrained activity and T(b) rhythms. During the daytime feeding schedule, all rats exhibited food anticipatory activity and T(b) rhythms that persisted during 2 days without food in constant dark. In some rats with partial or total DMH ablation, the magnitude of the anticipatory rhythm was weak relative to most intact rats. When mealtime was shifted to the late night, the magnitude of the food anticipatory activity rhythms in these cases was restored to levels characteristic of intact rats. These results confirm that rats can anticipate scheduled daytime or nighttime meals without the DMH. Improved anticipation at night suggests a modulatory role for the DMH in the expression of food anticipatory activity rhythms during the daily light period, when nocturnal rodents normally sleep.

Environmental context Phytoplankton form the base of marine food-webs, and hence they have been proposed as the likely source of many arsenic compounds found in marine animals. Because of the difficulties associated with field experiments with phytoplankton, attempts to test this hypothesis have relied mainly on laboratory experiments. This study assesses the environmental validity of this research approach by investigating the influence of the culturing experimental protocol on the uptake, accumulation and biotransformation of arsenic by marine phytoplankton. Abstract Arsenic cycling by the marine phytoplankton Dunaliella tertiolecta and the marine diatom Thalassiosira pseudonana was influenced by culture regime. Arsenic was associated with the residue cell fractions of batch cultured phytoplankton (D. tertiolecta and T. pseudonana), due to the accumulation of dead cells within batch cultures. Greater arsenic concentrations were associated with water-soluble and lipid-soluble cell fractions of continuously cultured phytoplankton. Arsenoribosides (as glycerol (Gly-), phosphate (PO4-) and sulfate (OSO3-)) were ubiquitous in D. tertiolecta (Gly- and PO4- only) and T. pseudonana (all three species). Additionally, arsenobetaine (AB) was not detected in any phytoplankton tissues, illustrating that marine phytoplankton themselves are not an alternate source of AB. Arsenic species formation was influenced by culture regime, with PO4-riboside produced under nutrient rich conditions, whereas Dimethylarsenoacetate (DMAA) was found in old (>42 days old) batch cultures, with this arsenic species possibly produced by the degradation of arsenoribosides-arsenolipids from decomposing cells rather than by biosynthesis. Nutrient availability, hence culture regime was thus influential in directly and indirectly influencing arsenic cycling and the arsenic species produced by D. tertiolecta and T. pseudonana. Future research should thus utilise continuous culture regimes to study arsenic cycling as these are far more analogous to environmental processes.

Circadian rhythms in rodents can be phase shifted by appropriately timed activity. This may be dependent on motivational context; running induced by a novel wheel is effective, whereas running induced by cold has been inferred to be ineffective. This issue was reexamined using a different cold exposure procedure. On the first day of constant dark, 6 h before usual dark onset, Syrian hamsters were exposed to cold (+/- 4 degrees C) in their home cages, or were confined to novel wheels for 3 h. Activity rhythms were significantly phase advanced by 92 +/- 10 min following cold exposure and 86 +/- 17 min following novel wheel running, compared to 13 +/- 18 min in a control condition. Most hamsters exhibited eating, drinking, and modest levels of wheel running (1367 +/- 292 counts/6 h) during and for 3 h after cold exposure. Phase shifts following cold were not affected by food and water deprivation but were significantly attenuated by locking the wheel for 6 h beginning at cold onset (24 +/- 12 min). These data indicate that cold-induced running, even at modest levels, is an effective nonphotic Zeitgeber and do not provide support for a hypothesis that motivational contexts determine the phase-shifting value of physical activity.

Evoked cerebral responses were recorded to brief shifts of patterned stimuli under conditions of constant luminous flux during voluntary eye movements and ocular fixation. Virtually complete suppression of evoked response and perception of the pattern shift occurred during eye movements. In contrast, much dimmer test flashes presented against a dark field were suppressed to a substantially lesser degree. Retinal blur was eliminated as a factor in saccadic suppression, since inhibition was the same for horizontally and vertically oriented patterns. The results indicate that an inhibitory mechanism must exist which is specific for contour shift as opposed to change in luminance.