Ecotoxicological evaluation of sodium fluoroacetate on aquatic organisms and investigation of the effects on two fish cell lines

Sodium monofluoroacetate (compound 1080) is one of the most potent pesticides. It is also a metabolite of many other fluorinated compounds, including anticancer agents, narcotic analgesics, pesticides or industrial chemicals. Other sources of water contamination are the atmospheric degradation of hydrofluorocarbons and hydrochlorofluorocarbons. However, there is little information available about the adverse effects of sodium fluoroacetate in aquatic organisms. Firstly, the bacterium Vibrio fischeri (decomposer), the alga Chlorella vulgaris (1st producer) and the cladoceran Daphnia magna (1st consumer) were used for the ecotoxicological evaluation of SMFA. The most sensitive models were C. vulgaris and D. magna, with a NOAEL of 0.1 and an EC50 of 0.5 mM at 72 h, respectively. According to the results after the acute exposure and due to its high biodegradation rate and low bioaccumulation potential, sodium fluoroacetate is most unlikely to produce deleterious effects to aquatic organisms. Secondly, two fish cell lines were employed to investigate the effects and mechanisms of toxicity in tissues from 2nd consumers. The hepatoma fish cell line PLHC-1 was more sensitive to SMFA than the fibroblast-like fish cell line RTG-2, being the uptake of neutral red the most sensitive bioindicator. Lysosomal function, succinate dehydrogenase and acetylcholinesterase activities were inhibited, glucose-6-phosphate dehydrogenase activity was particularly stimulated, and metallothionein and ethoxyresorufin-O-deethylase levels were not modified. Intense hydropic degeneration, macrovesicular steatosis and death mainly by necrosis but also by apoptosis were observed. Moreover, sulphydryl groups and oxidative stress could be involved in PLHC-1 cell death induced by SMFA more than changes in calcium homeostasis.     

The effect of biodiversity on the hantavirus epizootic

We analyze a mathematical model of the epizootic of Hantavirus in mice populations, including the effect of species that compete with the host. We show that the existence of the second species has an important consequence for the prevalence of the infectious agent in the host. When the two mice species survive in the ecosystem, the competitive pressure of the second species may lead to reduction or complete elimination of the prevalence of infection. The transition between the disappearance of the infection and its presence occurs at a critical value of the competitor's population, resembling a second-order phase transition in a statistical system. The results provide a rigorous framework for the study of the impact of biodiversity in the propagation of infectious diseases, and further lends itself to future experimental verification.     

Testosterone and sexual signalling in male house sparrows (Passer domesticus)

Female preference for mates with elaborated ornaments has often been explained on the basis that exaggerated secondary sexual traits might reflect individual quality and females might gather direct and indirect benefits in mating with such males. Sexual signals must however also entail costs to be reliable indicators of male quality. Androgens have been suggested as a physiological link between sexual signals and individual quality for several reasons, including their immunosuppressive effect. In this study, we tested two hypotheses linked to the hormonal basis of sexual signal expression. First, we investigated whether testosterone is correlated with the size of the black feather bib on the throat of male house sparrows (Passer domesticus) - a trait involved in intra- and inter-sexual selection. Second, we tested whether testosterone affects the seasonal exposure of the trait. Observational work conducted in 1998 showed that the testosterone level was positively correlated with badge size both in spring and in the subsequent fall, after molt. In 1999, we experimentally reduced spring testosterone levels using silastic implants filled with cyproterone acetate, an antiandrogen. Male house sparrows implanted with cyproterone acetate showed reduced exposure of the badge, because the white tips of the black feathers of the badge wore off later than in control males implanted with empty silastic tubes. This result suggests that testosterone can be causally involved in the expression of a secondary sexual trait in house sparrows, at least in terms of its seasonal exposure.     

Phylogeography of the sub-Antarctic notothenioid fish Eleginops maclovinus: evidence of population expansion

Phylogeography studies add insights into the geographic and evolutionary processes that underline the genetic divergence of populations. This work examines the geographic genetic structure of the Patagonian blennie, Eleginops maclovinus, a notothenioid (Perciformes) endemic to South American temperate and sub-Antarctic waters, using mitochondrial DNA cytochrome b sequences. We found 58 haplotypes in the analysis of 261 individual sequences of 833 base pairs in length. Among-population variance was very low (1.62%) and many haplotypes were shared between several populations across the species geographic range. Genetic differentiation was not consistent with a simple model of isolation by distance, possibly suggesting a lack of equilibrium between gene flow and local genetic drift. The analysis of mismatch distributions, neutrality tests, and the Bayesian Skyline Plot showed a pattern consistent with a recent population expansion event that may have taken place during the Middle Pleistocene.     

DYNAMIC RESPONSE OF AQUIFER SYSTEMS TO LOCALIZED RECHARGE1

ABSTRACT. The response of stream-unconfined aquifer systems to localized recharge is investigated by means of a two-dimensional finite element model. A variational approach is used in conjunction with the finite element method to solve the ground water flow equation. Linear approximated triangular elements are used to calculate the hydraulic head distribution in the flow region. The Crank-Nicholson centered scheme of numerical integration is employed to approximate the time derivative in the flow equation. A computer program is developed to calculate the hydraulic head distribution in the flow region. Solutions provided by the finite element model should prove useful in the evaluation of quantitative and qualitative changes in aquifer systems due to natural or artificial recharge. In addition, they should prove useful in the study of irrigation and drainage problems.     

Unexpected reproductive strategy of Sardinella aurita off the coast of Venezuela

Biological sampling of Spanish sardine (Sardinella aurita Valenciennes, 1847) off the coast of Venezuela from 1956 to 1989 was used to study the reproductive strategy and migration pattern of the population. Whereas in many pelagic fishes the energy re-allocation necessary for reproduction usually occurs optimally at the end of the upwelling season when planktonic production reaches a maximum, in the present study a 5 mo delay was observed. This suggests that energy was stored as lipids early in the season and released later via metabolism for gamete production. Major reproduction did not occur in an area and at a time when offshore transport and turbulence were low, which is also unusual for a pelagic fish species. These results are discussed in terms of the life cycle of the Spanish sardine and its possible migratory patterns. The reproductive strategy of this population apparently gives priority to optimising food availability for the offspring and not to preventing eggs and larvae being transported offshore. The presence of “retention” areas could explain this unexpected strategy. Received: 4 November 1996 / Accepted: 20 December 1996     

Severe bilateral renal disease: Correlation of antenatal and autopsy findings

We report 20 infants with severe bilateral renal disease examined by prenatal ultrasound and by autopsy. In 17, the prenatal and pathologic diagnoses correlated well. Although the prenatal and autopsy findings differed in the three remaining cases, the autopsy confirmed the presence of severe bilateral renal abnormalities. All 20 pregnancies were complicated by oligohydramnios, which was severe in 60 per cent. Most of these fetuses had malformation of other organ systems. This series supports the utility of prenatal ultrasound examinations, but emphasizes the need for postnatal evaluation of congenital renal disease including pathologic examination of tissue when possible for correct classification and genetic counselling.     

Leakage of nitrous oxide emissions within the Spanish agro-food system in 1961–2009

In this paper we examine the trends of nitrous oxide (N₂O) emissions of the Spanish agricultural sector related to national production and consumption in the 1961–2009 period. The comparison between production- and consumption-based emissions at the national level provides a complete overview of the actual impact resulting from the dietary choices of a given country and allows the evaluation of potential emission leakages. On average, 1.5 % of the new reactive nitrogen that enters Spain every year is emitted as N₂O. Production- and consumption-based emissions have both significantly increased in the period studied and nowadays consumption-based emissions are 45 % higher than production-based emissions. A large proportion of the net N₂O emissions associated with imported agricultural goods comes from countries that are not committers for the United Nations Framework Convention on Climate Change Kyoto Protocol Annex I. An increase in feed consumption is the main driver of the changes observed, leading to a remarkable emission leakage in the Spanish agricultural sector. The complementary approach used here is essential to achieve an effective mitigation of Spanish greenhouse gas emissions.     

Microbiological characterization and specific methanogenic activity of anaerobe sludges used in urban solid waste treatment

This study presents the microbiological characterization of the anaerobic sludge used in a two-stage anaerobic reactor for the treatment of organic fraction of urban solid waste (OFUSW). This treatment is one alternative for reducing solid waste in landfills at the same time producing a biogas (CH(4) and CO(2)) and an effluent that can be used as biofertilizer. The system was inoculated with sludge from a wastewater treatment plant (WWTP) (Río Frío Plant in Bucaramanga-Colombia) and a methanogenic anaerobic digester for the treatment of pig manure (Mesa de los Santos in Santander). Bacterial populations were evaluated by counting groups related to oxygen sensitivity, while metabolic groups were determined by most probable number (MPN) technique. Specific methanogenic activity (SMA) for acetate, formate, methanol and ethanol substrates was also determined. In the acidogenic reactor (R1), volatile fatty acids (VFA) reached values of 25,000 mg L(-1) and a concentration of CO(2) of 90%. In this reactor, the fermentative population was predominant (10(5)-10(6)MPN mL(-1)). The acetogenic population was (10(5)MPN mL(-1)) and the sulphate-reducing population was (10(4)-10(5)MPN mL(-1)). In the methanogenic reactor (R2), levels of CH(4) (70%) were higher than CO(2) (25%), whereas the VFA values were lower than 4000 mg L(-1). Substrate competition between sulphate-reducing (10(4)-10(5)MPN mL(-1)) and methanogenic bacteria (10(5)MPN mL(-1)) was not detected. From the SMA results obtained, acetoclastic (2.39 g COD-CH(4)g(-1)VSS(-1)day(-1)) and hydrogenophilic (0.94 g COD-CH(4)g(-1)VSS(-1)day(-1)) transformations as possible metabolic pathways used by methanogenic bacteria is suggested from the SMA results obtained. Methanotrix sp., Methanosarcina sp., Methanoccocus sp. and Methanobacterium sp. were identified.     

Increasing conservation management action by involving local people in natural resource monitoring

There is a need for a better understanding of the status of the environment. At the same time, concerns have been raised regarding alienation of the local populace from environmental decisions. One proposed solution is participatory environmental monitoring. When evaluating the usefulness of environmental monitoring, the focus may be on accuracy, as is usually done by scientists, or on efficiency in terms of conservation impact. To test whether investment in participatory biodiversity monitoring makes economic sense for obtaining data for management decisions, we compared the cost efficiency of participatory and conventional biodiversity monitoring methods in Philippine parks. We found that, from a government perspective, investment in monitoring that combines scientific with participatory methods is strikingly more effective than a similar level of investment in conventional scientific methods alone in generating conservation management interventions. Moreover, the local populace seemed to benefit from more secure de facto user rights over land and other resources. Participatory biodiversity monitoring not only represents a cost-effective alternative when conventional monitoring is impossible, but it is also an unexpectedly powerful complementary approach, capable of generating a much higher level of conservation management intervention, where conventional monitoring already takes place.