Electric Signals in the Social Behavior of Sympatric Elephantfish (Mormyridae, Teleostei) from the Upper Zambezi River

 Electrocommunication in mormyrid fish from African freshwaters is a challenging research field in neuroethology (Turner et al. 1999). However, virtually nothing is known about electrocommunication within natural mormyrid populations involving sympatric, syntopic species. Here we report on the nocturnal activities and electrocommunication among three syntopic species in a spacious laboratory setting resembling the natural one. Petrocephalus catostoma, Cyphomyrus discorhynchus, and Hippopotamyrus sp. nov. differ characteristically in their behavior, such as in territorial defense, schooling, and joining members of other species during foraging. Comparing social encounters within and between species, the first evidence for interspecific electrocommunication among syntopic species was found. Received: 27 September 1999 / Accepted in revised form: 22 December 1999     

Liebe Gutachterinnen und liebe Gutachter

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Hydroxyl radical generation by electron paramagnetic resonance as a new method to monitor ambient particulate matter composition

Epidemiological studies have demonstrated the relationship between exposure to ambient particulate matter (PM) and health effects in those with cardiopulmonary diseases. The free radical generating activity of particles has been suggested as a unifying factor in the biological activity of PM in toxicological studies but so far has not been applied as a method for environmental monitoring of PM. The purpose of this study was to characterize hydroxyl radical (OH*) production by different size fractions of PM, to use as an alternative method for monitoring of PM composition and activity. We have developed a method, using electron paramagnetic resonance (EPR), to measure OH* radical formation in suspensions of particles in the presence of hydrogen peroxide and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a specific spin-trap. Samples of ambient particulate matter (PM) of different size fractions were collected from various sites on various filters. PM deposited on filters as well as suspensions in water retain its ability to generate OH* and this generation is determined by concentration of hydrogen peroxide and soluble metals. However, large variations in OH* radical formation and kinetics were found with different soluble metals and within metals (Fe, V) with different valencies. The method was applied to environmental monitoring in Hettstedt-Zerbst, situated in South-Eastern Germany, where it showed a relation to Cu-content of PM. The method was also applied in Duisburg, where the PMI fraction showed the highest DMPO-OH* generation but was not linked to particle counts. The method integrates metal bioavailability and reactivity and can provide a better understanding of the effect of small variations in mass concentrations on health.