Prey detection in trawling insectivorous bats: duckweed affects hunting behaviour in Daubenton's bat, Myotis daubentonii

Daubenton's bat, a trawling vespertilionid bat species, hunts for insects that fly close to, or rest on, the water surface. During summer, many ponds at which Daubenton's bats hunt become gradually covered with duckweed. The purpose of this study was to investigate the effects of duckweed cover on the hunting behaviour of Daubenton's bats and on the ultrasound-reflecting properties of the water surface. Our study revealed the following. (1) Daubenton's bat avoids water surfaces covered with duckweed. (2) Prey abundance was related to the number of foraging Daubenton's bats but was independent of duckweed cover. (3) When mealworms were presented among standardized amounts of duckweed to naturally foraging Daubenton's bats, they caught significantly less mealworms when the duckweed cover was increased. (4) Measurements with ultrasonic signals show that a water surface covered with duckweed returns a much stronger background echo at small angles (i.e. parallel to the water surface) compared to an uncovered water surface. It seems likely that a cover of duckweed on the water surface interferes with prey detection by masking the echoes returning from prey. (5) It was relatively difficult for the bats to discriminate small patches of duckweed from mealworms. The proposed discrimination mechanism for this trawling bat species suggests that single duckweed patches can also be mistaken for natural prey by Daubenton's bats. Received: 4 January 1998 / Accepted after revision: 19 July 1998     

Reproductive patterns in the Antarctic brachiopod Liothyrella uva

The reproductive cycle of the Antarctic articulate brachiopod Liothyrella uva (Broderip, 1833) is described from monthly samples collected between September 1985 and July 1987 from a population at Signy Island, Antarctica. Spermatogenesis and oogenesis are described for the first time in this species. Surface dried-tissue masses for a standard individual (41 mm shell length) were calculated for the digestive diverticula, gut, lophophore and gonad from monthly dissections of 15 brachiopods. Seasonal patterns, with summer peaks, were observed in the digestive diverticula and gut. The lophophore and gonad masses did not exhibit seasonal trends. Females showed a sharp decrease in proportion of large oocytes between October and November in 1986, suggesting spawning during this period. There was no similar decrease during the same period in 1985. Mean percent spermatozoa measurements revealed a large increase in November 1985 and a rapid decline in December 1985. This suggested a large spawning event for males in 1985 which was not repeated the following year. These data indicate large inter-annual differences in reproductive activity as well as differences between males and females. They also suggest the possibility of sperm storage by females. Brood characteristics were also highly variable. The smallest brooding female was 31.5 mm in length. Some females brooded more than one developmental stage simultaneously, and variation in brood size (numbers of embryos or larvae held in the lophophore) and brood composition between individuals was high. All samples collected throughout the 2 yr period contained some females with broods. The data suggest that the reproductive strategy of L. uva is highly plastic, and that there may be three reproductive periodicities on seasonal, annual and inter-annual time scales. Received: 16 May 1997 / Accepted: 2 March 1998     

Cysteine-glutathione disulfide, the sperm-release pheromone of the marine polychaete Nereis succinea (Annelida: Polychaeta)

Summary. In the marine polychaete Nereis succinea (Frey & Leuckart 1847) a sex pheromone was isolated from the coelomic fluid of sexually mature females and identified by NMR studies and independent synthesis. This pheromone is released by the females during reproduction together with eggs and coelomic fluid into the free water column and induces sperm release of surrounding males. Its structure was ascertained as L-cysteine-glutathione disulfide. It exhibited a response threshold of 0.6 · 10⁻⁷ M. Received 15 July 1997; accepted 25 November 1997.     

On the origin of elevated levels of persistent chemicals in the environment

In general, contamination levels tend to be highest close to sources of a chemical and decline with increasing distance as a result of dilution, dispersion and degradation. However, contrary to this, circumstances have been described when contamination levels are higher further away from sources than at the sources themselves. Examples are elevated levels of persistent, hydrophobic, organic chemicals in the Arctic, in mountain regions and in forest soils. In order to address the questions of why and when such an inversion of environmental levels is occurring, this paper seeks to identify, name and categorise principles of general validity leading to such behaviour. By compiling and analysing various causes of elevated contamination levels in the environment, three main categories became apparent, 1. equilibrium partitioning effects, 2. effects resulting from changes in phase composition, volume or temperature, and 3. dynamic or kinetic effects. These principles are illustrated with several examples. The case can be made that understanding, quantifying and predicting these causes could provide a general conceptual framework for studying the fate of chemicals in the environment.     

Zur Humusausstattung ostbayerischer Mittelgebirgsböden

Background

Important properties and processes of soils are influenced by their humus contents. Therefore knowledge about the humus status of soils is an important requirement for a meaningful evaluation on dynamics and risk potentials.

Aim

Based on the extensive database of the Bavarian Environment Agency typical humus content and humus storage are compiled for soils of the Bavarian and Upper Palatinate Fores. Their importance for questions on soil and environment is estimated.

Results and Discussion

The evaluation revealed rising soil organic matter with an increasing cool and moist climate on the mountains of the Bavarian and Upper Palatinate Forest. This is particularly true for the mineral soil above 600 m above sea-level, where more organic matter is stored than in the humus layer. Depending on altitude the calculated total humus stock of soils varies between 12 and 40 kg^*m^?2, which means medium to very high humus contents. The highest humus stock occur between 900 and 1200 m above sea-level, where intensively rooted ‘Lockerbraunerden’ are prevailing. The somewhat lower humus content in soils above 1200 m above sea-level (about 5 kg^* m^?2) is explained by a shallow indurated horizon, that reduce the rooting to the upper 3–5 decimetres. The even though considerable humus stock of this concrete like indurated horizon is therefore explained by infiltration. The remarkable thickness of organic layers above 1200 m above sea-level is probably not only a result of climate, but also of a difficult decomposition of the prevailing spruce litters.

Conclusions

The high contents of organic matter in the examined soil should release appreciable amounts of CO₂ if there will be a change in climate. Furthermore a decomposition of humus may considerably worsen the supply with water and nutrients on these sites.     

The insurance market’s influence on investments in safety measures

In a risky process there are three alternative ways to treat the negative consequences of the risk or the accident. We can: (1) take all the consequences when an accidental event occurs, (2) reduce the probability and/or the consequences of an accidental event by safety measures or (3) transfer the consequences of the occurrence to parties better able to carry them (i.e. buying insurance). In safety management a prevailing practice is that access to an insurance market does not affect the investment in safety measures. In this paper we discuss what the consequences are of this common practice in relation to insurance and mandatory safety requirements. We conclude that an overinvestment in safety measures is very likely if insurance is not taken into account. Moreover, mandatory safety measures and insurance can lead to both over- and underinvestment in safety measures.     

The assessment of the soil–plant-animal transport of the risk elements at the locations affected by brown coal mining

Environmental Science and Pollution Research - The North Bohemian Brown Coal Basin (Czech Republic) is suggested as a source of significant pollution in the surrounding environment with various...     

Quantifying and mapping species threat abatement opportunities to support national target setting

The successful implementation of the Convention on Biological Diversity's post-2020 Global Biodiversity Framework will rely on effective translation of targets from global to national level and increased engagement across diverse sectors of society. Species conservation targets require policy support measures that can be applied to a diversity of taxonomic groups, that link action targets to outcome goals, and that can be applied to both global and national data sets to account for national context, which the species threat abatement and restoration (STAR) metric does. To test the flexibility of STAR, we applied the metric to vascular plants listed on national red lists of Brazil, Norway, and South Africa. The STAR metric uses data on species’ extinction risk, distributions, and threats, which we obtained from national red lists to quantify the contribution that threat abatement and habitat restoration activities could make to reducing species’ extinction risk. Across all 3 countries, the greatest opportunity for reducing plant species’ extinction risk was from abating threats from agricultural activities, which could reduce species’ extinction risk by 54% in Norway, 36% in South Africa, and 29% in Brazil. Species extinction risk could be reduced by a further 21% in South Africa by abating threats from invasive species and by 21% in Brazil by abating threats from urban expansion. Even with different approaches to red-listing among countries, the STAR metric yielded informative results that identified where the greatest conservation gains could be made for species through threat-abatement and restoration activities. Quantifiably linking local taxonomic coverage and data collection to global processes with STAR would allow national target setting to align with global targets and enable state and nonstate actors to measure and report on their potential contributions to species conservation.     

Stoichiometric controls of nitrogen and phosphorus cycling in decomposing beech leaf litter

Resource stoichiometry (C:N:P) is an important determinant of litter decomposition. However, the effect of elemental stoichiometry on the gross rates of microbial N and P cycling processes during litter decomposition is unknown. In a mesocosm experiment, beech (Fagus sylvatica L.) litter with natural differences in elemental stoichiometry (C:N:P) was incubated under constant environmental conditions. After three and six months, we measured various aspects of nitrogen and phosphorus cycling. We found that gross protein depolymerization, N mineralization (ammonification), and nitrification rates were negatively related to litter C:N. Rates of P mineralization were negatively correlated with litter C:P. The negative correlations with litter C:N were stronger for inorganic N cycling processes than for gross protein depolymerization, indicating that the effect of resource stoichiometry on intracellular processes was stronger than on processes catalyzed by extracellular enzymes. Consistent with this, extracellular protein depolymerization was mainly limited by substrate availability and less so by the amount of protease. Strong positive correlations between the interconnected N and P pools and the respective production and consumption processes pointed to feed-forward control of microbial litter N and P cycling. A negative relationship between litter C:N and phosphatase activity (and between litter C:P and protease activity) demonstrated that microbes tended to allocate carbon and nutrients in ample supply into the production of extracellular enzymes to mine for the nutrient that is more limiting. Overall, the study demonstrated a strong effect of litter stoichiometry (C:N:P) on gross processes of microbial N and P cycling in decomposing litter; mineralization of N and P were tightly coupled to assist in maintaining cellular homeostasis of litter microbial communities.