Fluxes of nutrients and trace metals across the sediment-water interface controlled by sediment-capping agents: bentonite and sand

The effect of bentonite and sand, as natural capping agents, on the fluxes of nutrients and trace metals across the sediment-water interface was studied through sediment incubation, and the ecotoxicological impact was assessed by using Daphnia magna. Bentonite and sand were layered on the sediment at 15, 75, and 225 mg cm(-2), and the concentration of cations, nutrients, and trace metals was measured. Sediment incubation showed that bentonite reduced the N flux but increased the P flux as a result of dissolution of non-crystalline P from bentonite, while sand slightly decreased the N fluxes but not the P flux. The concentration of Na increased in the overlying water with increasing application rates of bentonite, while that of Ca decreased. However, regardless of the rate of sand application, concentrations of all cation species remained unchanged. The concentration of As and Cr increased with bentonite application rate but decreased with sand. Both capping materials suppressed fluxes of Cd, Cu, Ni, and Zn compared to control, and the extent of suppression was different depending on the trace metal species and capping agents used. During sediment incubation, the survival rate of D. magna significantly decreased in bentonite suspension but began to decrease at the end in sand suspension. Sediment capping of mildly polluted sediments by using bentonite and sand lowered the level of nutrients and trace metals. However, unexpected or undesirable side effects, such as influxes of P and As from bentonite to the overlying water and a possibility of toxic impacts to aquatic ecosystems, were observed, suggesting that capping agents with an adequate assessment of their side effects and toxicity should be predetermined for site-specific sediment management strategies.clos

UV and camouflage in crab spiders (Thomisidae)

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Large-scale forward genetics screening identifies Trpa1 as a chemosensor for predator odor-evoked innate fear behaviors

Innate behaviors are genetically encoded, but their underlying molecular mechanisms remain largely unknown. Predator odor 2,4,5-trimethyl-3-thiazoline (TMT) and its potent analog 2-methyl-2-thiazoline (2MT) are believed to activate specific odorant receptors to elicit innate fear/defensive behaviors in naive mice. Here, we conduct a large-scale recessive genetics screen of ethylnitrosourea (ENU)-mutagenized mice. We find that loss of Trpa1, a pungency/irritancy receptor, diminishes TMT/2MT and snake skin-evoked innate fear/defensive responses. Accordingly, Trpa1 -/- mice fail to effectively activate known fear/stress brain centers upon 2MT exposure, despite their apparent ability to smell and learn to fear 2MT. Moreover, Trpa1 acts as a chemosensor for 2MT/TMT and Trpa1-expressing trigeminal ganglion neurons contribute critically to 2MT-evoked freezing. Our results indicate that Trpa1-mediated nociception plays a crucial role in predator odor-evoked innate fear/defensive behaviors. The work establishes the first forward genetics screen to uncover the molecular mechanism of innate fear, a basic emotion and evolutionarily conserved survival mechanism

Japanese encephalitis virus tropism in experimentally infected pigs.

Pigs are considered to be the main amplifying host for Japanese encephalitis virus (JEV), and their infection can correlate with human cases of disease. Despite their importance in the ecology of the virus as it relates to human cases of encephalitis, the pathogenesis of JEV in pigs remains obscure. In the present study, the localization and kinetics of virus replication were investigated in various tissues after experimental intravenous infection of pigs. The data demonstrate a rapid and broad spreading of the virus to the central nervous system (CNS) and various other organs. A particular tropism of JEV in pigs not only to the CNS but also for secondary lymphoid tissue, in particular the tonsils with the overall highest viral loads, was observed. In this organ, even 11 days post infection, the latest time point of the experiment, no apparent decrease in viral RNA loads and live virus was found despite the presence of a neutralizing antibody response. This was also well beyond the clinical and viremic phase. These results are of significance for the pathogenesis of JEV, and call for further experimental studies focusing on the cellular source and duration of virus replication in pigs

Olfactory Sensitivity for Six Predator Odorants in CD-1Mice, Human Subjects, and Spider Monkeys

Using a conditioning paradigm, we assessed the olfactory sensitivity of six CD-1 mice (Mus musculus) for six sulfurcontainingodorants known to be components of the odors of natural predators of the mouse. With all six odorants, themice discriminated concentrations ,0.1 ppm (parts per million) from the solvent, and with five of the six odorants the bestscoringanimals were even able to detect concentrations ,1 ppt (parts per trillion). Four female spider monkeys (Atelesgeoffroyi) and twelve human subjects (Homo sapiens) tested in parallel were found to detect the same six odorants atconcentrations ,0.01 ppm, and with four of the six odorants the best-scoring animals and subjects even detectedconcentrations ,10 ppt. With all three species, the threshold values obtained here are generally lower than (or in the lowerrange of) those reported for other chemical classes tested previously, suggesting that sulfur-containing odorants may play aspecial role in olfaction. Across-species comparisons showed that the mice were significantly more sensitive than the humansubjects and the spider monkeys with four of the six predator odorants. However, the human subjects were significantlymore sensitive than the mice with the remaining two odorants. Human subjects and spider monkeys significantly differed intheir sensitivity with only two of the six odorants. These comparisons lend further support to the notion that the number offunctional olfactory receptor genes or the relative or absolute size of the olfactory bulbs are poor predictors of a species’olfactory sensitivity. Analysis of odor structure–activity relationships showed that in both mice and human subjects the typeof alkyl rest attached to a thietane and the type of oxygen moiety attached to a thiol significantly affected olfactorysensitivity.Funding: The study was financially supported by a grant (J-51435-IV) from CONACYT Mexico (www.conacyt.mx) to LTHS. The funders had no role in study design,data collection and analysis, decision to publish, or preparation of the manuscript.</p