Electrosensory basis for individual recognition in a weakly electric, mormyrid fish, Pollimyrus adspersus (Günther, 1866)

Pollimyrus adspersus discriminates the individually variable waveforms of Electric Organ Discharges (EODs) of conspecifics of only 150–250 s duration. We examined: (1) the discrimination threshold for artificially generated EODs of similar waveform, (2) the mechanism of signal analysis (spectral vs temporal) present, by determining the discrimination between different waveforms of identical amplitude spectra, and (3) the threshold field intensity and reach of discrimination. The triphasic P. adspersus EOD waveform was artificially generated by superimposing two Gaussians, one wide, the second narrow, inverted, and of threefold amplitude. The natural variability among individual EOD waveforms was simulated by phase-shifting one Gaussian relative to the other. The symmetrical waveform where the peaks of the two Gaussians coincided was used as a reference (phase shift=0, rewarded stimulus S+). Results were: (1) in food-rewarded conditioning experiments, trained fish (N=7) detected a phase-shift in artificial EOD stimuli as low as 2 s (N=2 fish), 6 s (N=1) and 10 s (N=1). (2) All fish tested (N=3) discriminated between artificial EODs of identical amplitude spectra but different waveforms (hence, different phase spectra), demonstrating a temporal mechanism of signal analysis. (3) The maximum reach of waveform discrimination was 130 cm at 4.9 V_p-p/cm and 100 S/cm water conductivity (test signal generated at natural amplitude), that is, similar to the reach of EOD detection. Therefore, among the three kinds of electroreceptor organ present in mormyrids, we consider Knollenorgane the relevant sensory organs for EOD waveform discrimination.Communicated by J. Krause     

Social parasitism by honeybee workers (Apis mellifera capensis Esch.): evidence for pheromonal resistance to host queen’s signals

Social parasites exploit their host’s communication system to usurp resources and reproduce. In the honeybee, Apis mellifera, worker reproduction is regulated by pheromones produced by the queen and the brood. Workers usually reproduce when the queen is removed and young brood is absent. However, Cape honeybee workers, Apis mellifera capensis, are facultative intraspecific social parasites and can take over reproduction from the host queen. Investigating the manner in which parasitic workers compete with host queens pheromonally can help us to understand how such parasitism can evolve and how reproductive division of labour is regulated. In A. m. capensis, worker reproduction is associated with the production of queen-like pheromones. Using pheromonal contest experiments, we show that Apis mellifera scutellata queens do not prevent the production of queen-like mandibular gland compounds by the parasites. Given the importance of these pheromones in acquiring reproductive status, our data suggest that the single invasive lineage of parasitic workers occurring in the range of A. m. scutellata was selected for its superior ability to produce these signals despite the presence of a queen. Such resistance was indeed less frequent amongst other potentially parasitic lineages. Resistance to reproductive regulation by host queens is probably the key factor that facilitates the evolution of social parasitism by A. m. capensis workers. It constitutes a mechanism that allows workers to evade reproductive division of labour and to follow an alternative reproductive option by acquiring direct fitness in foreign colonies instead of inclusive fitness in their natal nests.     

Das OECD-Prüfrichtlinienprogramm

The Test Guideline of the OECD (organisation for Economic Co-operation and Development) is concerned with the international harmonisation of physicochemical, ecotoxicological and toxicological testing methods for chemicals and pesticides. New guidelines have been actualised and survey reports (Detailed Review Papers — DRP) dealing with test methods and the related questions have been compiled for the OECD member countries. The basic work to this international programme has occurred by way of the national co-ordinators who represent the interface between the national experts and the OECD bodies. The co-ordination of the Test Guidelines in Germany involves specific experts as well as the routine convention of working groups for exchanging the specific state of affairs and the respective strategies employed.     

Die Photosynthehemmung pflanzlicher Protoplasten

The ecotoxicological effect of rain water on the light-dependent, photosynthetical oxygen production of suspended protoplasts from the bean speciesVicia faba L. was used for the characterization of airborne immissions. The protoplast-biotest — with rain water samples taken in an agricultural area from March to July — showed a clear inhibition of the photosynthetical oxygen production. Simultaneously, chemical analyses on some herbicides were carried out. The concentrations determined, however, did not sufficiently explain the measured inhibition of oxygen production; so, the toxicity yielded was assumed to result from not-analyzed compounds as well as synergistic and additive effects of the rain water constituents.     

THE PRACTICE OF COMBINED SEWER SYSTEM MODELING1

ABSTRACT: A combined sewer system is a complex system subject to the dynamic stimuli of precipitation, runoff pollution loads, and sanitary wastes. The system response is a random series of pollutant loads to a receiving water. In many localities, these discharges create considerable water quality problems. Mathematical models can and have played a useful role in predicting the behavior of combined sewer systems and evaluating abatement strategies. Based on the authors' experiences over the past several years, this paper explores some of the positive and negative aspects of using deterministic mathematical models to simulate the behavior of combined sewer systems. A case study follows a discussion on modeling objectives, limitations of modeling, model selection, establishing model credibility, and many other considerations necessary in modeling and simulating these systems.     

Clarifying the definition ofSustainable agriculture

A number of distinct definitions ofsustainable agriculture have been proposed. In this paper we criticize two such definitions, primarily for conflating sustainability with other objectives such as economic viability and ecological integrity. Finally, we propose and defend a definition which avoids our objections to the other definitions.     

Reduction of Waste and Electricity Demand in The Netherlands: A Hypothetical Intervention

An important question in the present reorganization and liberalization of infrastructure networks in many countries is what kind of regulatory regimes can provide incentives for demand management and reduction in a future situation. In this paper, the present situation in the Dutch waste and electricity sectors is analysed. It is concluded that a quantity-based tariff system and the entwined interests of organizations are key impediments to effective demand management in these two sectors. A hypothetical intervention is proposed which aims to remove these two fundamental drawbacks. Some likely consequences of the suggested intervention are discussed.     

Aktive Stoffe als Handlungsoption gegen die Verschleppung von Organismen durch Seeschiffe?

Background and Scope

The marine shipping lanes have become the most important path for the invasion of foreign aquatic organisms. The increasing global trade results in an increase in the number of marine vessels. Without any protective measures, with every ship carrying foreign organisms the risk of biological invasions will rise.

Results

The International Martime Organization (IMO) of the United Nations developed a convention to reduce the transfer of organisms with ballast water. After the entry-into-force of this convention the fleet of the world has to be equipped with effective ballast water management technology before 2016. This article discusses potential options for action. To comply with the limit values of the ballast water convention, the current state of the art demands the use of active substances. Any decision on the approval of active substances used for ballast water treatment and the environmental impact assessment lies with the IMO. Proposed to day are UV-radiation, active chlorine, active oxygen, the creation of biocides through electrolysis and a change in gases contained in the ballast water. The technologies and the potential risks are presented.

Conclusions

Despite the introduction of an approval procedure by IMO any reliable assessment of the real risks involved in the use of biocides is impossible, as the risk assessment approaches have still to be developed. On the regulatory level, the main focus in data requirements for the risk assessment is on a comprehensive testing of the toxic potential of the biocides proposed. Strategies for the identification and evaluation of the chemical resulting from the treatment of limnic, marine and brackish water are not fully developed. An integrating assessment of risks involved in the introduction of foreign organisms versus the toxic effects of the substances used or created during treatment is still missing.     

Online electro-Fenton-mass spectrometry reveals 2,4′,5-trichlorobiphenyl oxidation products and binding to organic matter

Electrochemistry–mass spectrometry is used to simulate redox reactions in many research disciplines because this technique is fast and provides information on compound metabolites. However, the analysis of the degradation of refractory organic pollutants by reactive oxygen species is difficult to achieve by the electrochemistry step. Therefore, here we use online electro-Fenton-mass spectrometry to study for the first time the oxidation of 2,4′,5-trichlorobiphenyl [polychlorinated biphenyl (PCB) 31] by reactive oxygen species and the binding reactions of PCB degradation products with model substances of natural organic matter. The degradation products were identified by coupled Q Trap mass spectrometry. We observed a binding of a degradation product with γ-l-glutamyl-l-cysteinyl-glycine. We propose a transformation pathway. We conclude that online electro-Fenton-mass spectrometry is a promising technique to study the oxidation of refractory organic pollutants and further binding of degradation products with natural organic matter.