Dart receipt promotes sperm storage in the garden snail Helix aspersa

During courtship, many helicid snails attempt to pierce the body walls of their mating partners with mucus-coated calcareous darts. The mucus covering the dart induces conformational changes in the female reproductive tract of the recipient, closing off the entrance to the gametolytic bursa copulatrix. We have tested the effect of dart receipt on the number of sperm stored by once-mated snails, Helix aspersa. Snails that were hit by darts stored significantly more sperm than did snails that were missed. Additionally, the effect of the dart was stronger in smaller animals and the number of sperm stored decreased with the shell volume of the recipient. Although larger animals produced larger spermatophores, dart-shooting success was not related to the number of sperm transferred. These data suggest a role for dart-shooting in post-copulatory sexual selection.     

Population genetics of the Antarctic heteronemertean Parbolasia corrugatus from the South Orkney Islands

An allozyme survey, using starch-gel electrophoresis, was carried out on eight populations of the Antarctic nemertean worm Parborlasia corrugatus (McIntosh, 1876) collected from locations around the South Orkney Islands, Antarctica. These populations were separated by distances in the order of tens of kilometres. Genetic variation was estimated over 22 enzyme loci for all populations examined, giving an observed heterozygosity of 0.142. This was much lower than the expected heterozygosity (H _e  = 0.201), and it was found that there was a significant deficiency of het‐erozygotes across four enzyme loci ( p ≤ 0.01). A more detailed examination of this deficiency of heterozygotes was undertaken for the six populations and six variable enzyme loci for which the most complete data sets existed. A significant deficiency of heterozygotes was found at the enzyme locus Odh-1 for four of the six populations examined ( p ≤ 0.01). Mean F _is (0.240) indicated a significant ( p ≤ 0.01) within-population component of the heterozygote deficiency estimated for the six populations sampled, and this was mainly due to the␣Ap-1, Odh-1 and Pgm-1 loci. The mean F _st value (0.036) was also significant ( p ≤ 0.01), indicating a degree of genetic differentiation between populations. The observed levels of genetic differentiation between populations of P. corrugatus and the significant heterozygote deficiencies were unexpected, because this species has been reported to have a long-lived planktotrophic larva. It is hypothesised that recruitment of P. corrugatus in the South Orkney Islands originates from genetically distinct populations located in the Weddell Sea and to the west of the Antarctic Peninsula. Shifts in the relative position of the Weddell Sea Front, Weddell–Scotia Confluence and Scotia Front, relative to the South Orkney Islands, provide a mechanism for variation in the origin of recruits over time. Received: 24 July 1997 / Accepted: 31 October 1997     

Pendrin mediates uptake of perchlorate in a mammalian in vitro system

Perchlorate is a known endocrine disruptor present in groundwater, vegetables and dairy food products in many regions of the United States. It interferes with the uptake of iodide into the thyrocyte by the sodium-iodide symporter at the basolateral surface, thus potentially disrupting the synthesis of thyroid hormone. Because transport of iodide from the thyroid follicular cells to the follicular lumen is mediated by the protein pendrin at the apical surface, we hypothesized that perchlorate may also interact with this protein. Therefore, HeLa cells were transfected with the human SLC26A4 gene, which encodes pendrin, to generate an in vitro mammalian system expressing the recombinant pendrin protein (HeLa-PDS). The HeLa-PDS cells, along with untransfected cells, were then cultured in presence of iodide and/or perchlorate. Intracellular levels of these two chemicals were measured by ion chromatography tandem mass spectrometry. Results from this study show that iodide and perchlorate uptake increases significantly in HeLa-PDS cells as compared to untransfected cells. Thus, recombinant HeLa cells expressing pendrin protein accumulate iodide and perchlorate intracellularly, indicating that pendrin is involved in the uptake of perchlorate. Additional results from this study suggest that iodide and perchlorate competitively inhibit each other for uptake by pendrin. The ability of perchlorate to compete with iodide for uptake by both basal and apical transporters may increase the potential of perturbation of thyroid homeostasis and therefore the estimated risk posed to susceptible human populations.     

Conceptualization of a robust performance assessment and evaluation model for consolidating community water systems

Community water systems (CWS) face significant competing forces for change from decreasing water resource availability, stricter water quality regulations, decreasing federal subsidies, increasing public scrutiny, decreasing financial health, and increasing infrastructure replacement costs. These competing forces necessitate increasing consolidation responses among financially stressed CWS. Consolidation responses allow financially stressed CWS to increase levels of service by taking advantage of economy of scale benefits, such as eliminating service duplications across administration and operational functions. Consolidation responses also promote improved financial accountability among consolidating CWS, especially when operating as integral subsystems of a larger regional drinking water supply (RDWS) system. The goal of this paper is to propose a conceptual model for robust performance assessment and evaluation (PAE) among consolidating CWS. The objectives of this paper are to conceptualize methods for: (1) consistent performance assessment and (2) uniform summative performance evaluation among consolidating CWS. The expected outcome from implementing robust PAE among consolidating CWS is increased levels of service through transparent benchmarking and improved financial accountability. The proposed robust PAE model provides the basis for constructing decision support system (DSS) tools that estimate efficient solutions for allocating limited financial resources among consolidating CWS. The paper is a significant departure from current CWS PAE approaches in two ways. First, it provides a goal-oriented approach for robust PAE among consolidating CWS. Second, it constructs efficiency-based performance metrics to temporally and spatially monitor the degree of attainment of the RDWS systems' goal.     

2-Methylpyridine-N-oxidation runaway studies

Calorimetry has been used in order to identify the runaway behavior of 2-methylpyridine-N-oxidation (2-picoline-N-oxidation). Experiments were performed in an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC), employing 2-methylpyridine-N-oxide (2-picoline-N-oxide) with or without catalyst, 2-methylpyridine-N-oxide, hydrogen peroxide, 2-methylpyridine (2-picoline) and catalyst, and 2-methylpyridine, hydrogen peroxide and catalyst. Approximately 16.5 g of aqueous solutions were used in 100 ml closed glass cells in all but one measurement. Measurements were performed isothermally or employing the Heat-Wait-Search (HWS) technique. During reaction runaway, any excess of hydrogen peroxide and the produced 2-methylpyridine-N-oxide decompose releasing non-condensable gases and raising the pressure. It was found that the reaction runaway is condition-sensitive. Catalyst, the presence of 2-picoline and/or its N-oxide, affect hydrogen peroxide and/or 2-picoline-N-oxide decomposition rates. Further research accompanied by analytical measurements of the gas and liquid phase would provide indications in regard to the decomposition mechanisms followed in those cases.     

The impact of size on the fate and toxicity of nanoparticulate silver in aquatic systems

The increased use of silver nanomaterials presents a risk to aquatic systems due to the high toxicity of silver. The stability, dissolution rates and toxicity of citrate- and polyvinylpyrrolidone-coated silver nanoparticles (AgNPs) were investigated in synthetic freshwater and natural seawater media, with the effects of natural organic matter investigated in freshwater. When sterically stabilised by the large PVP molecules, AgNPs were more stable than when charge-stabilised using citrate, and were even relatively stable in seawater. In freshwater and seawater, citrate-coated AgNPs (Ag–Cit) had a faster rate of dissolution than PVP-coated AgNPs (Ag–PVP), while micron-sized silver exhibited the slowest dissolution rate. However, similar dissolved silver was measured for both AgNPs after 72 h in freshwater (500–600 μg L⁻¹) and seawater (1300–1500 μg L⁻¹), with higher concentrations in seawater attributed to chloride complexation. When determined on a mass basis, the 72-h IC50 (inhibitory concentration giving 50% reduction in algal growth rate) for Pseudokirchneriella subcapitata and Phaeodactylum tricornutum and the 48-h LC50 for Ceriodaphnia dubia exposure to Ag⁺ (1.1, 400 and 0.11 μg L⁻¹, respectively), Ag–Cit (3.0, 2380 and 0.15 μg L⁻¹, respectively) and Ag–PVP (19.5, 3690 and 2.0 μg L⁻¹, respectively) varied widely, with toxicity in the order Ag⁺ > Ag–Cit > Ag–PVP. Micron-sized silver treatments elicited much lower toxicity than ionic Ag⁺ or AgNP to P. subcapitata. However, when related to the dissolved silver released from the nanoparticles the toxicities were similar to ionic silver treatments. The presence of natural organic matter stabilised the particles and reduced toxicity in freshwater. These results indicate that dissolved silver was responsible for the toxicity and highlight the need to account for matrix components such as chloride and organic matter in natural waters that influence AgNP fate and mitigate toxicity.     

Apca Activities Continue to Show Growth and Expansion

The activities and accomplishments of the Air Pollution Control Association during 1974-1975 continued to show growth and expansion, although there was a decline in membership. We have a financial surplus to report in spite of the fact that our publications program was plagued with inflationary price increases in paper, printing and distribution.     

An Analysis of Regional Haze Using Tracers of Opportunity

A two-year record of hourly concentrations of halocarbon tracers (methylchloroform and perchloroethylene) and hourly averages of particle light scattering (B_sp) has been analyzed In an effort to understand the sources of haze In the U.S. southwestern deserts and mountains. Measurements were taken on top of Spirit Mountain in southern Nevada. In conjunction with photographs used to interpret visual quality, haze episodes at Spirit Mountain were usually coincident with elevated concentrations of tracers originating from urban sources. Haze obscured an 88-km-distant mountain 17 percent of the total observation time. Of those Incidents, 69 percent were associated with long-range transport of haze from the Los Angeles Basin.     

Mineralization of PAHs in coal-tar impacted aquifer sediments and associated microbial community structure investigated with FISH

The microbial community structure and mineralization of polycyclic aromatic hydrocarbons (PAHs) in a coal-tar contaminated aquifer were investigated spatially using fluorescence in situ hybridization (FISH) and in laboratory-scale incubations of the aquifer sediments. DAPI-detected microbial populations in the contaminated sediments were three orders of magnitude greater than nearby uncontaminated sediments, suggesting growth on coal-tar constituents in situ. Actinobacteria, beta- and gamma-Proteobacteria, and Flavobacteria dominated the in situ aerobic (>1 mg l(-1) dissolved oxygen) microbial community, whereas sulfate-reducing bacteria comprised 37% of the microbial community in the sulfidogenic region of the aquifer. Rapid mineralization of naphthalene and phenanthrene were observed in aerobic laboratory microcosms and resulted in significant enrichment of beta- and gamma-Proteobacteria potentially explaining their elevated presence in situ. Firmicutes, Flavobacteria, alpha-Proteobacteria, and Actinobacteria were also enriched in the mineralization assays, but to a lesser degree. Nitrate- and sulfate-limited mineralization of naphthalene in laboratory microcosms occurred to a small degree in aquifer sediments from locations where groundwater chemistry indicated nitrate- and sulfate-reduction, respectively. Some iron-limited mineralization of naphthalene and phenanthrene was also observed in sediments originating near groundwater measurements of elevated ferrous iron. The results of this study suggest that FISH may be a useful tool for providing a much needed link between laboratory microcosms and groundwater measurements made in situ necessary to better demonstrate the potential for natural attenuation at complex PAH contaminated sites.     

Tree species effect on the redistribution of soil metals

Phytostabilization of metals using trees is often promoted although the influence of different tree species on the mobilization of metals is not yet clear. Soil and biomass were sampled 33 years after planting four tree species (Quercus robur, Fraxinus excelsior, Acer pseudoplatanus, Populus 'Robusta') in a plot experiment on dredged sediment. Poplar took up high amounts of Cd and Zn and this was associated with increased Cd and Zn concentrations in the upper soil layer. The other species contained normal concentrations of Cd, Cu, Cr, Pb and Zn in their tissues. Oak acidified the soil more than the other species and caused a decrease in the concentration of metals in the upper soil layer. The pH under poplar was lower than expected and associated with high carbon concentrations in the top soil. This might be assigned to retardation of the litter decomposition due to elevated Cd and Zn concentrations in the litter.