Teil 1: PCDD/F in Böden,Vegetation und Kuhmilch

Soil samples were taken from residential gardens, grasslands and forests at 22 locations in Marsberg, North Rhine-Westphalia, and analyzed for PCDD/F. Sampling was concentrated on the vicinity of a former copper smelter where copper waste material (calledKieselrot) was deposited and emissions from former stacks contaminated a large land area. Maximum PCDD/F-concentrations were 407 ng TE GBA/kg dm in garden soil (0–30 cm depth), 98 ng TE BGA/kg dm in agricultural grassland (0–10 cm depth), 227 ng TE BGA/kg dm in wasteland, and up to 8073 ng TE BGA/kg dm in forest soils. PCDD/F-levels in soil decreased with increasing distance from the former sources providing a large historic emission problem, apart from the still existing kieselrot waste site. Ash residues from former flue gas duct showed up to 2,4 mg TE BGA/kg dm. PCDD/F-concentrations in vegetable samples from highly contaminated garden soils and grass from agricultural grassland were found to be relatively low in relation to soil values. PCDD/F-levels in salad showed a mean of 2,2 ng TE BGA/kg dm while grass concentrations were <6 ng TE BGA/kg dm. Thus, no correlation was found between soil and vegetation values with the exception for carrot roots where obviously a small transfer of PCDD/F between the two media took place. PCDD/F-content in grass taken over the vegetation period showed a tendency to increase toward the end of the growing season, which is probably related to changes in the dry matter yield over the season. No correlation was found in general between soil, grass and milk PCDD/F contents when all samples were taken from the same grassland. PCDD/F-concentrations in milk ranged between 0,6 and 1,1 pg TE BGA/g milkfat and were thus in the same range as consumer milk in the Federal Republic of Germany. PCDD/F in needles from conifers showed a clear relationship with respect to distance from the former waste site. The relatively high levels in conifer needles [36 ng TE BGA/kg dm] were obviously due to sporting activities (i.e. motocross racing where contaminated material was resuspended and deposited on surrounding trees).     

Growth and reproduction of Pycnogonum litorale (Pycnogonida) under laboratory conditions

The complete life cycle of Pycnogonum litorale Ström was observed under laboratory conditions. At 15?°C and a 16?h light:8?h dark photocycle, the duration of embryonic development from oviposition to egg-hatching varied from 32 to 111?d. The onset of egg hatching ranged from 32 to 81?d after oviposition in different egg batches, and the period between the first and the last hatch within a single egg batch varied between 16 and 57?d. The larval period, consisting of five larval instars, lasted between 66 and 113?d. Juvenile development required seven (exceptionally 8 or 9) moults and lasted between 263 and 400?d. The average interval between successive moults in juveniles increased with increasing size from 24 to 82?d. Though females did not moult more often than their male conspecifics, they reached a size from 8.5 to 11.0?mm (average 10.1?mm) while adult males measured only 7.0 to 8.5?mm (average 7.7?mm). At low temperatures (2?°C) moulting was almost completely inhibited. After raising the temperature to 6?°C, the moulting frequency increased to a rate almost as high as at a constant temperature of 15?°C. Moulting was also retarded by starvation and accelerated by subsequent feeding. Adults lived for up to 9?years without further moults, with several periods of mating and oviposition at irregular intervals. In combination with previous long-term field observations, the present results provide a more complete picture of the life cycle of P. litorale in a natural habitat. The great variation in the duration of the different developmental stages, the ability to survive periods of cold and starvation, and the longevity of the adults are important for the survival of pycnogonid populations under changing environmental conditions.     

Are naked and common mole-rats eusocial and if so, why?

Eusociality in mammals is defined in the present paper by the following criteria: reproductive altruism (which involves reproductive division of labor and cooperative alloparental brood care), overlap of adult generations, and permanent (lifelong) philopatry. We argue that additional criteria such as the existence of castes, colony size, reproductive skew, and social cohesion are not pertinent to the definition of eusociality in mammals. According to our definition of mammalian eusociality, several rodent species of the African family Bathyergidae can be considered eusocial, including the naked mole-rat (Heterocephalus glaber), Damaraland mole-rat (Cryptomys damarensis), and several additional, if not all, species in the genus Cryptomys. Furthermore, some species of social voles (like Microtus ochrogaster) may also fulfill criteria of mammalian eusociality. Understanding the evolution of eusociality in mole-rats requires answers to two primary questions: (1) What are the preconditions for the development of their eusocial systems? (2) Why do offspring remain in the natal group rather than dispersing and reproducing? Eusociality in mammals is by definition a special case of monogamy (more specifically: monogyny one female breeding), involving prolonged pair bonding for more than one breeding period. We argue that eusociality in mole-rats evolved from a monogamous mating system where cooperative brood care was already established. A tendency for group living is considered to be an ancestral (plesiomorph) trait among African bathyergid mole-rats, linking them to other hystricognath rodents. A solitary lifestyle seen in some genera, such as Bathyergus, Georychus, and Heliophobius, is assumed to be a derived trait that arose independently in different lineages of bathyergids, possibly as a consequence of selective constraints associated with the subterranean environment. In proximate terms, in eusocial mole-rats either puberty is assumed to be developmentally delayed so that under natural conditions most animals die before dispersal is triggered (e.g., in the case of Heterocephalus) or dispersal is induced only by an incidental encounter with an unfamiliar, yet adequate sexual partner (e.g., in the case of Cryptomys). Ultimately, a combination of strategies involving either dispersal and/or philopatry can be beneficial, especially in a highly unpredictable environment. If genetic relatedness among siblings is high (e.g., a coefficient of relatedness of 0.5 or more), then philopatry would not invoke an appreciable loss of fitness, especially if the cost of dispersing is higher than staying within the natal group. High genetic relatedness is more likely in a monogamous mating system or a highly inbred population. In this paper, we argue that the preconditions for eusociality in bathyergid mole-rats were a monogamous mating system and high genetic relatedness among individuals. We argue against the aridity food-distribution hypothesis (AFDH) that suggests a causal relationship between cooperative foraging for patchily distributed resources and the origin of eusociality. The AFDH may explain group size dynamics of social mole-rats as a function of the distribution and availability of resources but it is inadequate to explain the formation of eusocial societies of mole-rats, especially with respect to providing preconditions conducive for the emergence of eusociality.     

Learning from local knowledge: modeling the pastoral-nomadic range management of the Himba, Namibia.

It is widely accepted that successful grazing management strategies in semiarid ecosystems need to be adapted to the highly temporal and spatially heterogeneous forage production. Nevertheless, a full understanding of the key factors and processes for sustainable adaptive management has yet to be reached. The investigation of existing, successful range management systems by simulation models may help to derive general understanding and basic principles. The semi-nomadic Himba in northern Namibia applied a sophisticated management system until the mid-1990s which combined season-dependent pasture use (resulting in rainy-season pastures and dry-season pastures), preservation of reserves for drought and sanctions for rule breaking. A stochastic ecological simulation model has been developed here which represents the main aspects of this management system. With this model we analyze (1) which components of the traditional Himba strategy are essential for sustainability and (2) what happens to the state of the rangeland system under socioeconomic changes. This study shows that temporally and spatially heterogeneous pasture use yields higher productivity and quality of a pasture area than the pressure of homogeneous permanent grazing. Two aspects are of importance: (1) intra-annual heterogeneous use (resting of the dry-season pastures during the rainy season) and (2) interannual heterogeneous use (spatial extension of grazing in years of drought). This management system leads to an effective build-up and use of a buffer in the system: the reserve biomass (the non-photosynthetic reserve organs of the plants), an indicator for grazing and management history. Analyzing purchase as one form of socioeconomic change, we demonstrate that easier market access to purchase livestock may lead to a decline in vegetation quality. However, cattle production increases as long as rest periods on parts of the pasture during the rainy season are granted. Methodologically, we emphasize that simulation models offer an excellent framework for analyzing and depicting basic principles in sustainable range management derived from local knowledge. They provide the opportunity of testing whether these basic principles are also valid under different ecological and socioeconomic settings.     

Gentoxische Substanzen in Wässern

Waste waters with genotoxic potential are produced in various technical processes. Diffuse sources such as traffic and agriculture as well as point sources as mining, power plants, waste and waste water treatment facilities may emit water which shows mutagenic activity in bacteria test systems. A variety of compounds is known as mutagenes but in case studies it was not possible to assign the mutagenic potential of water to specific compounds. The chlorination and ozonation of drinking water may also generate genotoxic and cancerogenic compounds but at present it is not possible to assess the health risk of various drinking water disinfection methods.     

Variability in grazer-mediated defensive responses of green and red macroalgae on the south coast of South Africa

Variabilities in the responses of several South African red and green macroalgae to direct grazing and the responses of one green alga to cues from grazers were tested. We used two feeding experiments: (1) testing the induced responses of three red and one green algae to direct grazing by mesograzers and (2) a multi-treatment experiment, in which the direct and indirect effects of one macrograzer species on the green alga Codium platylobium were assessed. Consumption rates were assessed in feeding assays with intact algal pieces and with agar pellets containing non-polar extracts of the test algae. Defensive responses were induced for intact pieces of Galaxaura diessingiana, but were not induced in pellets, suggesting either morphological defence or chemical defence using polar compounds other than polyphenols. In contrast, exposure to grazing stimulated consumption of Gracilaria capensis and Hypnea spicifera by another grazing species. In the multi-treatment experiment, waterborne cues from both grazing and non-grazing snails induced defensive algal traits in C. platylobium. We suggest that inducible defences among macroalgae are not restricted to brown algae, but that both the responses of algae to grazers and of grazers to the defences of macroalgae are intrinsically variable and complex.     

Effects of fertilization and elevated CO<Subscript>2</Subscript> on larval food and butterfly nectar amino acid preference in<Emphasis Type="Italic"> Coenonympha pamphilus</Emphasis> L.

The effects of larval diet on the nutritional preferences of butterflies has rarely been examined. This study investigates whether alterations in the larval diet result in changes in adult preferences for nectar amino acids. Larvae of Coenonympha pamphilus were raised on fertilized or unfertilized Festuca rubra, grown under ambient (350 ppm) or elevated (750 ppm) atmospheric CO ₂environments. Fertilization led to marked increases in leaf nitrogen concentration. In plants grown under elevated CO ₂conditions, leaf water and nitrogen concentrations were significantly lower, and the C/N-ratio increased significantly. Fertilization of the host plant shortened the development time of C. pamphilus larvae, and pupal weight increased. In contrast, larvae of C. pamphilus developed significantly slower on F. rubra grown under elevated CO ₂, but adult emergence weight was not affected by CO ₂treatment of the plant. C. pamphilus females showed a clear preference for nectar mimics containing amino acids, whereas males, regardless of treatment, either preferred the nectar mimic void of amino acids or showed no preference for the different solutions. Female butterflies raised on fertilized plants showed a significant decline in their preference for nectar mimics containing amino acids. A slight, but not significant, trend towards increased nectar amino acid preference was found in females raised on plants grown under elevated CO ₂. We clearly demonstrate that alterations in larval host quality led to changes in butterfly nectar preferences. The ability of the butterfly to either rely less on nectar uptake or compensate for poor larval conditions represents a trade-off between larval and adult butterfly feeding.     

Time-dependent shifts between infanticidal and parental behavior in female burying beetles a mechanism of indirect mother-offspring recognition

Summary Female burying beetles Necrophorus vespilloides Herbst (Coleoptera: Silphidae) were allowed to lay eggs on a carcass and their subsequent behavior towards larvae added to the carcass was observed. Females did not discriminate against unrelated larvae if these were added within an hour after the females' own first larva had hatched (at the right time). Changing the spatial surroundings of the carcass had no effect on the females' readiness to exhibit care behavior. Neither did the age of the larvae added or the condition of the carcass affect the onset of maternal care. However, the females' response to larvae encountered was strongly time-dependent: most females killed and ate larvae that could not have hatched from their own eggs because they were added long before their own larvae hatched. The proportion of females accepting larvae added to early increased as the time their own larvae hatched approached. Larvae added to the carcass 2 or 3 days after the test females' own first larva had hatched were always accepted by females that had already started to feed larvae, but were often killed by females that were not feeding larvae. In the latter group of females, the tendency to kill larvae added was most pronounced if the females had already started to produce a second clutch of eggs at the time larvae were added. Offprint requests to: J.K. Müller