Egg incubation temperature affects male reproductive success but not display behaviors in lizards

The complex ritualized displays of males in many territorial species suggest that selection has shaped male behaviors in ways that affect fitness. In this study, we evaluated the link between display behavior during male–male interactions and reproductive success in the Australian jacky dragon (Amphibolurus muricatus), a lizard species that uses a complex series of movement patterns for communication. We quantified variation in male display behaviors by using video playback experiments in the laboratory, and subsequently assessed variation in male reproductive success by paternity analyses of offspring. Because the lizards used in this study came from eggs incubated under three thermal environments, we also could evaluate the impact of developmental temperature on adult behavior and reproductive success. Incubation temperature had a strong effect on male reproductive success; males produced under intermediate temperatures sired more offspring than those produced under extreme developmental temperatures. However, incubation temperature did not affect male display behavior, nor was male behavior associated with reproductive success. Our findings do not support the common assumption that display behaviors used during male–male interactions affect reproductive success.     

A Comparison of Loch Chemistry from 1955 and 1999 in the Cairngorms,N.E. Scotland

The Cairngorms in north-east Scotland is remote from pollutant sources although it currently receives ca. 10 kg ha¹ yr¹ S and ca. 11 kg ha¹ yr¹ N deposition from the atmosphere.In 1955, 15 lochs (lakes) at a range of altitudes were sampled and analysed for major ion concentrations. A new survey of these and an additional 23 lochs and their catchment soils was conducted in 1999 to determine the impact of acid deposition, and the changes in loch chemistry since the 1955 survey. The bedrock geology of this region has a strong influence on the loch chemistry. Surface waters were generally more acidic in high altitude areas due to predominantly poorly buffered, thin alpine soils developed on granitic parent material (mean acid neutralising capacity (ANC) for 23 lochs = 30 eq L¹). At lower altitudes where the geology is dominated by Dalradian metamorphic rocks surface waters are comparatively base rich and have higher ANC (mean ANC for 15 lochs = 157 eq L¹). Surface water nitrate concentrations show a negative relationship with soil C:N status, in that higher nitrate only occurs at low soil C:N ratios. A comparison of data for 1955 and 1999 shows that sulphate concentrations are significantly lower (67.8 and 47.5 eq L¹, respectively), and pH has improved (pH 5.6 and 5.9) in response to decreased S deposition since the mid 1970s. However, mean nitrate concentrations were found to increase from 2.48 >eq L¹ in 1955 to 5.65 eq L¹ in 1999. Differences in the sampling and laboratory methods from 1955 and 1999 are acknowledged in the interpretation of data.     

Policy uses of particulate exposure estimates

This paper reviews the uses of particulate exposure estimates for science and policy. We propose a set of normative factors to guide the selection and application of various approaches for exposure assessment. For exposure estimates intended for use in support of the development or air pollution regulations or selection of control strategies, the proposed criteria include--compatibility with policy scope and scale, cost-effectiveness, characterization of uncertainty, political and institutional feasibility, and sensitivity to framing. For exposure assessment in support of epidemiological research, key criteria are-compatability with the specific hypothesis being tested, and compatibility with the temporal and spatial scale of analysis. The various major approaches for estimation of exposure--direct and indirect measurement, empirical and physical modeling--are catalogued and compared with these proposed criteria.     

non-lethal responses of the freshwater snail potamopyrgus antipodarum to dissolved arsenic

Two non-lethal responses, avoidance andimmobility, were observed for thefreshwater gastropod Potamopyrgusantipodarum on exposure to dissolvedarsenic (As) as arsenate (As(V)) orarsenite (As(III)). Two differentpopulations of P. antipodarum, onewith a long history of exposure todissolved As from geothermal fluids andthe other with minimal exposure, werecompared to test for adaptation to As. Both snail populations avoided dissolvedAs(III), the more toxic form, at lowerconcentrations than As(V). As(V), theless toxic form, was avoided by both snailpopulations at much lower concentrationsthan those at which the snails becameimmobile. In contrast, the concentrationsof As(III) which caused avoidance werealmost the same as those which causedimmobility, implying that avoidance may notbe an effective response to protect thesesnails from exposure to As(III). Snailsfrom the exposed population avoided As(V)at about 20% of the concentration thatwas avoided by the snails from theunexposed population. At higherconcentrations of As(V) which causedimmobility, this difference in sensitivitypersisted up to an exposure time of 48 hours. After 96 hours exposure, however,both populations showed similarsensitivity. Snails from the exposedpopulation were more sensitive to As(III),both avoiding the As and becoming immobileat lower concentrations than were observedfor the same responses in the snails fromthe unexposed population. We suggest thatthe differences in sensitivity between thetwo populations could have been the resultof the higher soft body As burden of theexposed snails at the start of thelaboratory experiments.     

Reconstructing pre-acidification pH for an acidified Scottish loch: a comparison of palaeolimnological and modelling approaches

We reconstruct the pre-acidification pH of the Round Loch of Glenhead for 1800 AD using three diatom-pH transfer functions and a diatom-cladocera modern analogue technique (MAT), and compare these palaeo-data with hindcast data for the loch using the dynamic catchment acidification model MAGIC. We assess the accuracy of the transfer functions by comparing pH inferences from contemporary sediment and sediment trap diatom samples from the lake with measured pH from the UK Acid Waters Monitoring Network. The results from the transfer functions estimate the pH in 1800 to have been between 5.5. and 5.7, the MAT approach estimates pH at 5.8 and the MAGIC hindcast (for 1850) is pH 6.1. Whilst we have no independent method of assessing which of these values is most accurate, the disagreement between the two approaches indicates that further work is needed to resolve the discrepancies.     

The influence of water vapour on the determination of glutaraldehyde vapour concentrations using an electrochemical fuel cell sensor

The effects of relative humidity (40-90% RH) and varying glutaraldehyde vapour concentrations (< 0.1 ppm) on the response of an electrochemical fuel cell sensor have been investigated over time (0-400 s). These studies have identified changes in the response of the fuel cell with time after sampling. In particular, it has been found that the maximum cell output for water vapour occurs ca. 10 s after sampling whilst the response to glutaraldehyde occurs much later (> 100 s). For mixtures containing different ratios of water and glutaraldehyde vapours, the time taken to reach maximum fuel cell response varies between 10 and 100 s, depending on the ratio of the two vapours. For instance, glutaraldehyde vapour containing higher % RH has been found to result in shorter times to reach maximum fuel cell response. A comparison was made between measuring glutaraldehyde vapour concentrations in the presence of water vapour at the maximum fuel cell response and also at a fixed interval (240 s) after sampling. Such a comparison resulted in a reduction in the standard error from 36% to 5% for a glutaraldehyde vapour sample (0.023 ppm) measured at different values of relative humidity (40 to 80%). Examination of the effect of the sample volume (30-60 ml) on the response of the fuel cell shows, as expected, an approximate doubling of the fuel cell response. Optimisation of the fuel cell measurement parameters to measure a 60 ml sample leads to a lowering of the limit of detection from 0.083 ppm (for data taken at the maximum cell response) to 0.017 ppm for data measured 240 s after sampling. In the light of recent reductions in the legal limits for exposure to glutaraldehyde, this has important implications for the measurement of glutaraldehyde vapour in the workplace.     

Time-lapse 3-D seismic imaging of shallow subsurface contaminant flow

This paper presents a physical modelling study outlining a technique whereby buoyant contaminant flow within water-saturated unconsolidated sand was remotely monitored utilizing the time-lapse 3-D (TL3-D) seismic response. The controlled temperature and pressure conditions, along with the high level of acquisition repeatability attainable using sandbox physical models, allow the TL3-D seismic response to pore fluid movement to be distinguished from all other effects. TL3-D seismic techniques are currently being developed to monitor hydrocarbon reserves within producing reservoirs in an endeavour to improve overall recovery. However, in many ways, sandbox models under atmospheric conditions more accurately simulate the shallow subsurface than petroleum reservoirs. For this reason, perhaps the greatest application for analogue sandbox modelling is to improve our understanding of shallow groundwater and environmental flow mechanisms. Two fluid flow simulations were conducted whereby air and kerosene were injected into separate water-saturated unconsolidated sand models. In both experiments, a base 3-D seismic volume was recorded and compared with six later monitor surveys recorded while the injection program was conducted. Normal incidence amplitude and P-wave velocity information were extracted from the TL3-D seismic data to provide visualization of contaminant migration. Reflection amplitudes displayed qualitative areal distribution of fluids when a suitable impedance contrast existed between pore fluids. TL3-D seismic reflection tomography can potentially monitor the change in areal distribution of fluid contaminants over time, indicating flow patterns. However, other research and this current work have not established a quantifiable relationship between either normal reflection amplitudes and attenuation and fluid saturation. Generally, different pore fluids will have unique seismic velocities due to differences in compressibility and density. The predictable relationships that exist between P-wave velocity and fluid saturation can allow a quantitative assessment of contaminant migration.     

Hatching asynchrony and survival of insurance offspring in an obligate brood reducing species,the American white pelican

American white pelicans (Pelecanus erythrorhynchos) lay two eggs but typically rear only one young owing to siblicidal brood reduction affecting the later-hatched, or B-chick. When the A-offspring fails at an early age, the B-chick may survive as a replacement (insurance) offspring. Using a combination of nests with natural and artificially manipulated hatching asynchrony, I examined the hypothesis that hatching asynchrony in this species is adaptively tuned to permit B-chicks to survive during the time they are most likely to be needed as replacements, with brood reduction following when they become redundant. Hatching asynchrony over the natural range of 0–4 days significantly increased within-brood mass differentials and reduced B-chick lifespan. Full synchrony had a marginally negative effect on A-chick mass. Greater asynchrony did not significantly affect the number of days B-chicks survived after hatching of the A-chick, owing to a corresponding extension of time B-offspring were protected from harassment while still within the egg. This resulted in a high probability (> 0.8) of B-chicks surviving through the initial period (5–7 days) of maximum early A-chick loss. Redundant B-chicks were subject to heavy brood reduction, with both chicks likely to have survived at only one each of 94 natural and 84 manipulated (0, 2, and 4 days asynchrony) nests. Hatching asynchrony in American white pelicans, in combination with a rapid development of senior chick siblicidal competence, appears to result in a time course of brood reduction appropriate for an effective insurance reproductive strategy. Received: 2 February 1996 /Accepted after revision: 18 May 1996     

Upstream Channel Changes Following Dam Construction and Removal Using a GIS/Remote Sensing Approach1

Abstract: This study used an innovative GIS/remote sensing approach to study historical river channel changes in the Huron River, a wandering gravel‐bedded river in northern Ohio. Eight sets of historical aerial photographs (1958‐2003) span the construction of a low‐head dam (1969), removal of the spillway (1994), and removal of the dam itself (2002). Construction of the dam modified stream gradients >4 km upstream of the small impounded reservoir. This study tracked changes in the polygon size, shape, and centroid position of 12 sand‐gravel bars through a study reach 0.2‐4.1 km upstream of the dam. These bars were highly responsive, tending to migrate obliquely downstream and toward the outer bank at rates up to 9 m/year. Historical changes in the size and position of the bars can be interpreted as the downstream translation of one or more sediment waves. Prior to dam construction, a sediment wave moved downstream through the study reach. Following construction of the dam, this sediment wave became stationary and degraded in situ by dispersion. The growth of bars throughout the study reach during this time interval resulted in a progressive increase in channel sinuosity. Removal of the spillway rejuvenated downstream translation of a sediment wave through the study reach and was followed by a reduction in channel sinuosity. These results illustrate that important geomorphologic changes can occur upstream of low‐head dams. This may be a neglected area of research about the effects of dams and dam removals.     

No evidence for sperm priming responses under varying sperm competition risk or intensity in guppies

Sperm competition theory predicts that males should tailor their investment in ejaculates according to the number of rival males competing to fertilize a female’s eggs. Research spanning several taxa supports this prediction by showing that males are often sensitive to the level of sperm competition and adjust their investment in sperm numbers accordingly. More recent work has revealed that males may also tailor the quality of sperm according to the number of males competing for fertilization. Here I test for both effects in guppies (Poecilia reticulata) in an experiment that simultaneously evaluates the risk and intensity models of sperm competition. The experiment determined whether male guppies adjust the number (stripped ejaculate size) and quality (sperm velocity and viability) of sperm that are primed over a 3-day period according to experimental changes in the perceived level of sperm competition. A total of 136 focal males were initially stripped of all retrievable sperm and assayed for these sperm traits before being allocated at random to one of four treatments simulating different levels of sperm competition risk and intensity. During the 3-day treatment phase, focal males had visual and olfactory access to a sexually receptive (initially virgin) female maintained with different numbers of stimulus males to simulate variation in the risk and intensity of sperm competition. Following this, males were assayed again for the sperm traits. Contrary to predictions, there was no significant change in any of the measured variables among treatments, although qualitatively the patterns for sperm velocity and viability did conform to expectation. The lack of any trend for the number of sperm primed was unequivocal and future work examining the effects of sperm competition on sperm production should focus on whether males differentially allocate sperm numbers among matings that differ in the level of sperm competition.