Atlantic mollies (Poecilia mexicana) inhabit a variety of surface habitats, but they also occur in a sulfur cave in southern Mexico. We examined male mate choice
relative to female body size in the cave population and in the most closely related surface-dwelling population from a nearby
river. Males from both populations were either light- or dark-reared and could choose between two differently sized females
either on the basis of visual cues in light or on the basis of solely nonvisual cues in darkness. Sexual preferences were
estimated from the degree of association. Cave molly males always showed a preference for the larger female, both in light
and in darkness. Among the surface males, only light-reared males showed a preference in the visual cues test, but not in
darkness. In a control experiment, we demonstrated that male association preferences directly translate into actual mating
preferences. Apparently, using visual cues for mate choice is the ancestral state in this system, and using nonvisual cues
has evolved as a novel trait in the cave population. We discuss the evolution of nonvisual male mate choice in the context
of changed environmental conditions, namely the absence of light, hypoxia, and toxic hydrogen sulfide in the cave. 相似文献
In this study, the effect of dissolved organic carbon (DOC) derived from macroalga (Sargassum) on the acute toxicity of copper (Cu) and cadmium (Cd) to a freshwater cladoceran (Daphnia magna) was investigated. Potassium-loaded macroalga was incubated with ultrapure water to extract macroalgal DOC, which was then spiked with the constituents of the Elendt M7 hard water media. The 48 h median lethal concentration of Cu increased linearly with DOC levels but that of Cd was relatively independent of DOC levels (0-44 mg l(-1)). The independence of Cd toxicity on DOC level might be due to the competitive effect of high calcium concentrations in the media with Cd for the binding sites of DOC. The decreased Cu toxicity was a result of reduced Cu uptake as evidenced in a separate accumulation test. Also, the capability of the macroalgal DOC on reducing Cu toxicity was found to be comparable to DOC tested in other studies. Therefore, the present study suggested that the biosorption treatment process using macroalgae should consider the effect of DOC release from the biomass as a step of modifying the metal toxicity as well as influencing metal biosorption capacity. 相似文献
Concentrations of 22 trace elements were determined in green turtle (Chelonia mydas) eggs collected from Hong Kong. Concentrations of selenium, lead and nickel in these eggs were generally higher than those reported in other studies. The predicted no effect concentrations (PNEC; ng/g wet weight) of Pb (1000), Se (340 and 6000 for the worst-case and best-case scenarios, respectively) and Ni (17) in the green turtle eggs were estimated. Hazard quotients (HQs) estimate that Se (HQs: 0.2-24.5) and Ni (HQs: 4.0-26.4) may pose some risks to the turtles. Our study also found that concentrations of Ag, Se, Zn, Hg and Pb in the shell of the turtle eggs were significantly correlated with levels in the whole egg contents (yolk+albumen). Once the precise relationships of specific elements are established, egg-shell concentrations may be used as a non-lethal, non-invasive, surrogate for predicting whole egg burden of certain contaminants in marine turtles. 相似文献
Background, Aim and Scope
In this paper recent results are provided of an investigation on the discovery of 12 perfluorinated surfactants (PS) in different
surface and drinking waters (Skutlarek et al. 2006 a, Skutlarek et al. 2006 b). In the last years, many studies have reported
ubiquitous distribution of this group of perfluorinated chemicals, especially perfluorooctane sulfonate (PFOS) and perfluorooctanoic
acid (PFOA) in the environment, particularly in wildlife animal and human samples (Giesy and Kannan 2001, Houde et al. 2006,
Prevedouros et al. 2006). Perfluorinated surfactants (e.g. PFOS and PFOA) have shown different potentials for reproductory
interference and carcinogenity in animal experiments as well as partly long half-lives in humans (Guruge et al. 2006, FSA
UK 2006a, FSA UK 2006b, 3M 2005, OECD 2002, Yao and Zhong 2005). They possess compound-dependent extreme recalcitrance against
microbiological and chemical degradation and, in addition, they show variable potentials for bioaccumulation in animals and
humans (Houde et al. 2006).
Materials and Methods:
Surface and drinking water samples were collected from different sampling sites:
- Surface waters: samples taken from the rivers Rhine, Ruhr, Moehne and some of their tributaries. Further samples were taken
from the Rhine-Herne-Canal and the Wesel-Datteln-Canal.
- Drinking waters: samples taken in public buildings of the Rhine-Ruhr area.
After sample clean-up and concentration by solid-phase extraction, the perfluorinated surfactants were determined using HPLC-MS/MS.
Results:
All measured concentrations (sum of seven mainly detected components) in the Rhine river and its main tributaries (mouths)
were determined below 100 ng/L. The Ruhr river (tributary of the Rhine) showed the highest concentration (94 ng/L), but with
a completely different pattern of components (PFOA as major component), as compared with the other tributaries and the Rhine
river. Further investigations along the Ruhr river showed remarkably high concentrations of PS in the upper reaches of the
Ruhr river and the Moehne river (tributary of the Ruhr) (Ruhr: up to 446 ng/L, Moehne: up to 4385 ng/L). The maximum concentration
of all drinking water samples taken in the Rhine-Ruhr area was determined at 598 ng/L with the major component PFOA (519 ng/L).
Discussion:
The surface water contaminations most likely stem from contaminated inorganic and organic waste materials (so-called 'Abfallgemisch').
This waste material was legally applied to several agricultural areas on the upper reaches of the Moehne. Perfluorinated surfactants
could be detected in some suchlike soil samples. They contaminated the river and the reservoir belonging to it, likely by
superficial run-off over several months or probably years. Downstream, dilution effects are held responsible for decreasing
concentrations of PS in surface waters of the Moehne and the Ruhr river. In analogy to the surface water samples, PS (major
component PFOA) can be determined in many drinking water samples of the Rhine-Ruhr area where the water supplies are mainly
based on bank filtration and artificial recharge.
Conclusions:
The concentrations found in drinking waters decreased with the concentrations of the corresponding raw water samples along
the flow direction of the Ruhr river (from east to west) and were not significantly different from surface water concentrations.
This indicates that perfluorinated surfactants are at present not successfully removed by water treatment steps.
Recommendations and Perspectives:
Because of their different problematic properties (persistence, mobility, toxicity, bioaccumulation), the concentrations of
specific perfluorinated surfactants and their precursors in drinking waters and food have to be minimised. Therefore, it is
of utmost importance to take the initiative to establish suitable legal regulations (limitations/ban) concerning the production
and use of these surfactants and their precursors. Furthermore, it is indispensable to protect water resources from these
compounds. A discussion on appropriate limit values in drinking water and foodstuffs is urgently needed. Concerning the assumed
soil contamination, the corresponding regulation (Bioabfall-Verordnung 1998 – Regulation on Organic Waste 1998) should be
extended to allow the control of relevant organic pollutants. 相似文献
Loss of filtration efficiency in a fabric filter baghouse is typically caused by bag failure, in one form or another. The degree of such failure can be as minor as a pinhole leak or as major as a fully involved baghouse fire. In some cases, local air pollution regulations or federal hazardous waste laws may require estimation of the total quantity of particulate matter released to the environment as a result of such failures. In this paper, a technique is presented for computing the dust loading in the baghouse exhaust when one or more bags have failed. The algorithm developed is shown to be an improvement over a previously published result, which requires empirical knowledge of the variation in baghouse pressure differential with bag failures. An example calculation is presented for a baghouse equipped with 200 bags. The prediction shows that a small percentage of failed bags can cause a relatively large proportion of the gas flow to bypass the active bags, which, in turn, leads to high outlet dust loading and low overall collection efficiency from the baghouse. 相似文献
This paper explores the level of vulnerability to the hazard of fire that exists in Makola Market in Accra, Ghana, and assesses how this threat can be reduced through a community‐based risk assessment. It examines the perceptions of both market‐stall occupants and primary stakeholders regarding the hazard of fire, and analyses the availability of local assets (coping strategies) with which to address the challenge. Through an evaluation of past instances of fire, as well as in‐depth key stakeholder interviews, field visits, and observations, the study produces a detailed hazard map of the market. It goes on to recommend that policymakers consider short‐to‐long‐term interventions to reduce the degree of risk. By foregrounding the essence of holistic and integrated planning, the paper calls for the incorporation of disaster mitigation measures in the overall urban planning process and for the strict enforcement of relevant building and fire safety codes by responsible public agencies. 相似文献
Fish protein hydrolysates are digested form of protein with various bioactive properties where, the cleavages of molecular bonds of proteins can be broken by the enzymatic and chemical process. In this study, antioxidant properties of spray dried protein hydrolysate prepared from Pangasius viscera by using enzymatic (papain and pepsin), and chemical methods (hydrochloric acid and sodium hydroxide) were evaluated. Among the different treatments, pepsin-derived visceral protein hydrolysate showed the maximum antioxidant activity when used at higher concentrations. Essential amino acids (EAA) and hydrophobic amino acids are higher in papain-derived visceral protein hydrolysate. In pepsin-derived visceral protein hydrolysate, major proportion was contributed by glycine (Gly), glutamine (Glu), proline (Pro), and asparagine (Asp). Higher amount of aromatic amino acids are found in alkali-derived FVPH. Scanning electron microscopy (SEM) images of pepsin fish visceral protein hydrolysate showed better globular structure than the other treatments. It can be concluded that among the different treatments, the visceral protein hydrolysate prepared with pepsin had better overall quality regarding antioxidant properties and papain in nutritional point of view.