Postnatal nutrition influences male attractiveness and promotes plasticity in male mating preferences

Poor early-life nutrition could reduce adult reproductive success by negatively affecting traits linked to sexual attractiveness such as song complexity. If so, this might favor strategic mate choice, allowing males with less complex songs to tailor their mating tactics to maximize the reproductive benefits. However, this possibility has been ignored in theoretical and empirical studies. By manipulating the micronutrient content of the diet (e.g., low or high) during the postnatal period of male zebra finches, we show for the first time (1) that males reared on a poor (low) micronutrient diet had less complex songs as adults; (2) that these males, in contrast to the high micronutrient diet group, were more selective in their mating strategies, discriminating against those females most likely to reduce their clutch size when paired with males having less complex songs; and (3) that by following different mating strategies, males reared on the contrasting diets obtained similar reproductive benefits. These results suggest that early-life dietary conditions can induce multiple and long-lasting effects on male and female reproductive traits. Moreover, the results seem to reflect a previously unreported case of adaptive plasticity in mate choice in response to a nutritionally mediated reduction in sexual attractiveness.     

Effect of field exposure to 38-year-old residual petroleum hydrocarbons on growth, condition index, and filtration rate of the ribbed mussel, Geukensia demissa

In September 1969, the Florida barge spilled 700,000 L of No. 2 fuel oil into the salt marsh sediments of Wild Harbor, MA. Today a substantial amount, approximately 100 kg, of moderately degraded petroleum remains within the sediment and along eroding creek banks. The ribbed mussels, Geukensia demissa, which inhabit the salt marsh creek bank, are exposed to the spilled oil. Examination of short-term exposure was done with transplantation of G. demissa from a control site, Great Sippewissett marsh, into Wild Harbor. We also examined the effects of long-term exposure with transplantation of mussels from Wild Harbor into Great Sippewissett. Both the short- and long-term exposure transplants exhibited slower growth rates, shorter mean shell lengths, lower condition indices, and decreased filtration rates. The results add new knowledge about long-term consequences of spilled oil, a dimension that should be included when assessing oil-impacted areas and developing management plans designed to restore, rehabilitate, or replace impacted areas.     

Effect of two major N-nitroso hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) metabolites on earthworm reproductive success

Soil and topical tests were employed to investigate the effect of two N-nitroso metabolites of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) on earthworm reproduction. The lowest observed effect concentration (LOEC) for cocoon production and hatching was 50mg/kg for both hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) in soil. MNX and TNX also significantly affected cocoon hatching in soil (p<0.001) and in topical tests (p=0.001). The LOECs for cocoon hatching were 1 and 10mg/kg for MNX and TNX in soil, respectively, and 10mg/L in the topical test. Greater than 100mg/kg MNX and TNX completely inhibited cocoon hatching. In soil, the EC20 values for MNX were 8.7 and 8.8mg/kg for cocoon and juvenile production, respectively, compared to 9.2 and 9.1mg/kg for TNX, respectively. The EC20 values for the total number of cocoon hatchlings were 3.1 and 4.7mg/kg for MNX and TNX, respectively, in soil and 4.5 and 3.1mg/L in the topical test. Both MNX and TNX inhibited cocoon production and hatching, suggesting that they may have a negative affect on soil ecosystems at contaminated sites.     

Effect of vegetation type on throughfall deposition and seepage flux

This paper compares different vegetation types (coniferous and deciduous forest, grassed and pure heathland) in terms of input (throughfall deposition) and output (seepage flux) in a region with intermediate nitrogen load (+/-20kg Nha(-1)y(-1) via bulk precipitation) in comparable conditions in north Belgium. Coniferous forest (two plots Pinus sylvestris and two plots Pinus nigra) received significantly higher nitrogen and sulphur throughfall deposition than deciduous forest and heathland. Grassed and pure heathland had significantly highest throughfall quantities of Ca(2+) and Mg(2+), respectively. The observed differences in throughfall deposition between the different vegetation types were not univocally reflected in the ion seepage flux. Considerable seepage fluxes of NO(3)(-), SO(4)(2-), Ca(2+) and Al(III) were only found under the P. nigra plots. We discuss our hypothesis that the P. nigra forests already evolved to a situation of N saturation, while the other vegetation types did not.     

Prediction of Pb speciation in concentrated and dilute nutrient solutions

Despite the presence of numerous studies in the literature examining the phytotoxicity of Pb, there is a lack of precise quantitative data on limiting concentrations of Pb for plant growth. Using the PhreeqcI chemical equilibrium model, simulations were conducted to examine the speciation of Pb in concentrated and dilute nutrient solutions. Due to the higher P concentration of Hoagland's solution (1000microM), precipitation of chloropyromorphite (Pb5(PO4)3Cl) was predicted to occur at lower pH values, and at lower Pb concentrations, than for a dilute nutrient solution (2microM P). Although nutrient solutions prepared in the glasshouse were supersaturated (and Pb concentrations were substantially higher than predicted by modeling), they confirmed the importance of the P concentration in influencing the precipitation of Pb. Given the low solubility of Pb-phosphates, nutrient solutions with low P concentrations should be utilized, and plant growth should be related to measured Pb concentrations rather than to the quantity of Pb initially added.     

A directional passive air sampler for monitoring polycyclic aromatic hydrocarbons (PAHs) in air mass

A passive air sampler was developed for collecting polycyclic aromatic hydrocarbons (PAHs) in air mass from various directions. The airflow velocity within the sampler was assessed for its responses to ambient wind speed and direction. The sampler was examined for trapped particles, evaluated quantitatively for influence of airflow velocity and temperature on PAH uptake, examined for PAH uptake kinetics, calibrated against active sampling, and finally tested in the field. The airflow volume passing the sampler was linearly proportional to ambient wind speed and sensitive to wind direction. The uptake rate for an individual PAH was a function of airflow velocity, temperature and the octanol-air partitioning coefficient of the PAH. For all PAHs with more than two rings, the passive sampler operated in a linear uptake phase for three weeks. Different PAH concentrations were obtained in air masses from different directions in the field test.     

Empirical and simulated critical loads for nitrogen deposition in California mixed conifer forests

Empirical critical loads (CL) for N deposition were determined from changes in epiphytic lichen communities, elevated NO(3)(-) leaching in streamwater, and reduced fine root biomass in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) at sites with varying N deposition. The CL for lichen community impacts of 3.1kg ha(-1) year(-1) is expected to protect all components of the forest ecosystem from the adverse effects of N deposition. Much of the western Sierra Nevada is above the lichen-based CL, showing significant changes in lichen indicator groups. The empirical N deposition threshold and that simulated by the DayCent model for enhanced NO(3)(-)leaching were 17kg N ha(-1) year(-1). DayCent estimated that elevated NO(3)(-) leaching in the San Bernardino Mountains began in the late 1950s. Critical values for litter C:N (34.1), ponderosa pine foliar N (1.1%), and N concentrations (1.0%) in the lichen Letharia vulpina ((L.) Hue) are indicative of CL exceedance.     

Mercury biomethylation assessment in the estuary of Bilbao (North of Spain)

The relationship between the microbial methylation of mercury and the microbial activities in sediments and water collected from the estuary of Bilbao (North of Spain) was studied in three different sampling points and in two different seasons. Three different cultures were prepared with a sediment slurry to distinguish between biotic and abiotic methylation pathways and the variations of the methylmercury concentration and the variations of the population of total number of bacteria (TDC), anaerobic heterotrophic bacteria (AHB), sulphate-reducing bacteria (SRB) and Desulfovibrio were measured. From this work, it can be concluded that the variation of MeHg concentrations is a result of the methylation/demethylation processes in the sediments, and that the abiotic processes have a negligible contribution to those processes. According to the statistical analysis of the results (partial least squares analysis) a significant statistical correlation was established between methylmercury and the SRB counts.     

Potentiality of different isolates of wilt fungus Fusarium oxysporum collected from rhizosphere of tomato against root-knot nematode Meloidogyne incognita

This investigation was undertaken to determine the effect of culture filtrates of different isolates of Fusarium oxysporum f. sp. lycopersici on mortality of Meloidogyne incognita juveniles and egg hatching. It was observed that different concentrations including standard extract (S.E), 1:10 and 1:100 dilutions of all fungal filtrates inhibited egg hatch when compared with control. Minimum mortality and maximum hatching was observed in BRT (showing least mortality) isolate of F. oxysporum, while maximum mortality and minimum egg hatching was recorded in BGT (showing maximum mortality) isolate. Larval mortality was decreased with a decrease in concentration and the least mortality was observed in 1:100 when compared with SE and 1:10. The potentiality of both the isolates (BRT and BGT) against root-knot nematode M. incognita was confirmed by the pathogenicity test on tomato. These observations confirmed that F. oxysporumisolates possesses variability in pathogenicity ranging from pathogenic to bio-control agent. The plants inoculated with BRT isolate failed to show wilt symptoms while plants inoculated with BGT isolate showed wilt indices.     

In-field variation in 2,4-D mineralization in relation to sorption and soil microbial communities

This study was undertaken to assess 2,4-D mineralization in an undulating cultivated field, along a sloping transect (458 m to 442 m above sea level), as a function of soil type, soil microbial communities and the sorption of 2,4-D to soil. The 2,4-D soil sorption coefficient (Kd) ranged from 1.81 to 4.28 L kg(-1), the 2,4-D first-order mineralization rate constant (k) ranged from 0.04 to 0.13 day(-1) and the total amount of 2,4-D mineralized at 130 days (M(130)) ranged from 24 to 39%. Both k and M(130) were significantly negatively associated (or correlated) with soil organic carbon content (SOC) and Kd. Both k and M(130) were significantly associated with two fatty-acid methyl esters (FAME), i17:1 and a18, but not with twenty-two other individual FAME. Imperfectly drained soils (Gleyed Dark Grey Chernozems) in lower-slopes showed significantly lesser 2,4-D mineralization relative to well-drained soils (Orthic Dark Grey Chernozems) in mid- and upper-slopes. Well-drained soils had a greater potential for 2,4-D mineralization because of greater abundance and diversity of the microbial community in these soils. However, the reduced 2,4-D mineralization in imperfectly drained soils was predominantly because of their greater SOC and increased 2,4-D sorption, limiting the bioavailability of 2,4-D for degradation. The wide range of 2,4-D sorption and mineralization in this undulating cultivated field is comparable in magnitude and extent to the variability of 2,4-D sorption and mineralization observed at a regional scale in Manitoba. As such, in-field variations in SOC and the abundance and diversity of microbial communities are determining factors that require greater attention in assessing the risk of movement of 2,4-D by runoff, eroded soil and leaching.