The cabbage seedpod weevil,
Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), is a widely distributed invasive pest of cruciferous crops in North America. Control measures rely mostly ...on the application of insecticides but alternative control strategies such as classical biological control are under evaluation. To investigate the impact of parasitoids and other mortality factors on
C. obstrictus populations, life table studies were conducted between 2005 and 2007 in 13 winter oilseed rape fields in Switzerland, part of the native range. Under field conditions females only realized approximately 50% of their potential lifetime fecundity, varying between 96 and 631 eggs per individual. Total generational mortality was higher than 99.6% in each year. Overwintering mortality of adults was the major population limiting factor, contributing approximately 50% to the overall generational mortality of
C. obstrictus, whereas factors acting on the immature stages were responsible for the remaining 50%. Among the mortality factors of the immature stages, egg, larval and pupal mortality contributed 9–12%, 25–28% and 4–6% to the generational mortality, respectively. Larval ecto-parasitism on its own accounted for 7–15% of the generational mortality. Comparison of life table data presented here with that from North America will be invaluable for elucidating the mortality factors that regulate
C. obstrictus populations in Europe, the region of origin.
The three South African Territories (SAT) types of foot-and-mouth disease virus (FMDV) display great genetic and antigenic diversity, resulting from the independent evolution of these viruses in ...different geographical localities. For effective control of the disease in such areas, the use of custom-made vaccines is required. To circumvent the tedious process of vaccine strain selection, an alternative in the control process is being investigated. Specifically, it is proposed to replace the antigenic determinants of an infectious genome-length cDNA copy of a good SAT vaccine strain with those of appropriate field strains, producing custom-made FMDV chimeras for use in vaccine production. Here the construction of an infectious genome-length cDNA copy of the SAT2 vaccine strain, ZIM/7/83, is described, created utilizing an exchange-cassette strategy with an existing A(12) genome-length cDNA clone. The virus derived from this cDNA (designated vSAT2) displayed excellent growth properties in cell culture, indicating its potential usefulness in the production of custom-made vaccine strains. Evaluation of the growth of various SAT2/A12 chimeras created during the derivation of SAT2 infectious cDNA suggested incompatibilities between the non-structural proteins of ZIM/7/83 and the 5' UTR of A(12).
In the marine environment, settling particulates have been widely studied for their role as effective vertical transporters of nutrients and metals scavenged from the euphotic zone to the benthos. ...These particulates are composed of transparent exopolymers, plankton and bacterial cells, detritus and organic matter, and form various size fractions from colloids (<0.2μm) to aggregates, and finally marine snow (>300 μm). As marine snow forms in the water column, anoxic layers form around and within the aggregation potentially creating a prime environment for the methylation of mercury (Hg), which occurs primarily in low oxygen environments. To examine this process, marine aggregates were produced from sieved estuarine seawater (100 μm) in 1-L glass bottles spiked with stable isotope enriched methylmercury (CH
Hg) and inorganic mercury (
Hg(II)) at 18° C using a roller-table. After the rolling period, different particle-size fractions were collected and analyzed, including: visible marine snow (>300μm), particulates 8 to 300 μm, and particulates 0.2 to 8μm. Particulate analysis indicated higher incorporation of both forms of Hg into marine snow compared to unrolled treatments, with greater incorporation of
Hg(II) than CH
Hg. In addition, inorganic Hg was methylated and CH
Hg was demethylated in the larger particulate fractions (>8μm). Methylation and demethylation rates were assessed based on changes in isotopic composition of Hg(II) and CH
Hg, and found to be comparable to methylation rates found in sediments. These results indicate that net Hg methylation can occur in marine snow and smaller aggregates in oxic coastal waters, and that this net formation of CH
Hg may be an important source of CH
Hg in both coastal and open ocean surface environments.
The fate and mobility of mercury, and its bioaccumulation primarily as methylmercury (MeHg), in marine ecosystems are influenced by climate related environmental factors, including increased ...temperature and carbon loading. To investigate the interactions between sediment organic carbon and temperature MeHg bioaccumulation, mesocosm experiments were conducted examining relationships between sediment, water column and biota (sediment-dwelling amphipod and juvenile oyster) MeHg concentration. Experimental treatments consisted of a two by two design of high and low temperature (15 & 25 °C) and high and low sediment organic carbon (4–5% and 13% LOI, pre-experiment). Sediment organic carbon had significant individual effects on MeHg concentration in water and biota, with higher carbon associated with lower MeHg. Temperature individual effects were significant for sediment, water, and only amphipod MeHg concentration, with higher temperature treatments indicating higher MeHg concentration. There were significant temperature × carbon interactions observed for sediment, dissolved, and oyster MeHg concentration. Sediment carbon reduction had greater influence than temperature on increasing MeHg concentrations in both the water column and biota. MeHg concentrations in the bulk sediment were not correlated with MeHg in the water column or in the biota, indicating that even when sediments are the only source of MeHg, bulk sediment measurements do not provide a good proxy for bioaccumulation and that the concentration in bulk sediments is not the primary determinant of MeHg entry into the food web.
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•Climate change is predicted to influence carbon loading and temperature in estuaries.•Estuaries are important areas for methylmercury production and bioaccumulation.•Mesocosms examined effect of temperature and sediment organic carbon on MeHg.•Water column MeHg, not sediment concentration, related to biota MeHg•Sediment carbon influenced MeHg bioaccumulation more than temperature
Synopeas myles
(Walker) (Hymenoptera: Platygastridae) is a parasitoid of the swede midge,
Contarinia nasturtii
(Kieffer) (Diptera: Cecidomyiidae), in Europe. We conducted the first thorough ...investigation of this parasitoid’s biology. Contrary to the biology reported for all platygastrids to date, exposure of late-instar host larvae to parasitism as opposed to eggs or early larvae yielded more
S. myles
offspring. Superparasitism was relatively common in the field and among groups of females in the laboratory, but was much less common among single females, providing preliminary evidence for self-discrimination. Observation of immature stages of
S. myles
inside living hosts revealed that supernumerary larvae in superparasitized hosts were probably eliminated by physical combat soon after hatching. With increasing levels of superparasitism, sex ratios of offspring became more female-biased and their mean development time increased. The probability that offspring would emerge from a host and the size of offspring were unaffected by increasing levels of superparasitism.
West Nile virus (WNV), the leading cause of viral encephalitis in the United States, is an arthropod-transmitted member of the family
Flaviviridae. We have explored the interaction of this ...positive-strand RNA virus with signaling pathways involved in induction of the host's innate immune response. Phosphorylation of STAT-1 in response to interferon (IFN) treatment and the ability of IFN to establish an antiviral state were reduced in WNV replicon-bearing cell lines. Similarly, the activation of IRF3 and stimulation of IFN-β transcription in response to the double-stranded RNA (dsRNA) mimetic poly(I:C) were inhibited in replicon-bearing and WNV-infected HeLa cells. In contrast, WNV replicons did not affect IRF3 activation by Sendai virus infection, suggesting that not all IRF3 activating pathways are inhibited by WNV. Taken together, these findings demonstrate that WNV replication in cultured cells interferes with both the response to IFN and synthesis of IFN-β in response to dsRNA.
Reactive gaseous Hg (RGHg), usually assumed to be HgCl2, may dominate the total Hg depositional flux due to its higher surface reactivity and water solubility. Three methods are currently used for ...RGHg sampling: multistage filter packs, refluxing mist chambers, and KCI-coated denuders, but none of these methods are considered standard. Field comparisons were performed at Chesapeake Biological Laboratory (CBL) to test if these methods could give comparable results. Mist chambers and denuders were operated continuously for 24 h in some cases to observe the diurnal variation. All methods demonstrated the dynamic fluctuation of atmospheric RGHg, ranging from a few picograms per cubic meter to more than 500 pg/m3. These methods also reported similar temporal RGHg trends. At low RGHg levels, the denuder tended to report higher values of RGHg relative to the filter pack, while mist chamber values were generally in agreement with the filter pack. Discrepancy among methods was more significant under higher RGHg levels. Considering the uncertainties associated with these methods, our data suggest that these methods did produce comparable results. The 24-h continuous measurements showed that RGHg was usually undetectable at night. However, our data also suggest factors in addition to photochemistry, such as movement and mixing of air masses, are influencing the distribution of RGHg at CBL.
Striatal dopamine release is key for learning and motivation and is composed of subregions including the dorsal striatum (DS), nucleus accumbens core, and the nucleus accumbens shell. Spontaneously ...occurring dopamine release was compared across these subregions. Dopamine release/uptake dynamics differ across striatal subregions, with dopamine transient release amplitude and release frequency greatest in male mice, and the largest signals observed in the DS. Surprisingly, female mice exhibited little regional differences in dopamine release for DS and nucleus accumbens core regions, but lower release in the nucleus accumbens shell. Blocking voltage‐gated K+ channel (Kv channels) with 4‐aminopyridine enhanced dopamine detection without affecting reuptake. The 4‐aminopyridine effects were greatest in ventral regions of female mice, suggesting regional differences in Kv channel expression. The dopamine transporter blocker cocaine also enhanced detection across subregions in both sexes, with greater overall increased release in females than males. Thus, sex differences in dopamine transmission are apparent and likely include differences in the Kv channel and dopamine transporter function. The lack of regional differences in dopamine release observed in females indicates differential regulation of spontaneous and evoked dopamine release.
Spontaneous dopamine release, which is thought to be cholinergic dependent, was examined throughout the striatum in the context of sex in mice. Females exhibited similar release amplitude across regions, and males exhibited greater release in the dorsal striatum (DS) and accumbens shell (NAcs) versus core (NAcc). Clearance was slower and more variable in females across regions. Blocking Kv channels and dopamine transporters increased release throughout regions, with greatest effects in females. Blocking K+ channels did not reduce dopamine uptake. This work defines the major sex differences in dopamine across the striatum, with implications for sex‐dependent differences in motivation and associative learning.
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