Vapour pressures, aqueous solubility, Henry's law constants and air/water partition coefficients of 1,8-dichlorooctane and 1,8-dibromooctane

New data on the vapour pressures and aqueous solubility of 1,8-dichlorooctane and 1,8-dibromooctane are reported as a function of temperature between 20 °C and 80 °C and 1 °C and 40 °C, respectively. For the vapour pressures, a static method was used during the measurements which have an estimated uncertainty between 3% and 5%. The aqueous solubilities were determined using a dynamic saturation column method and the values are accurate to within ±10%. 1,8-Dichlorooctane is more volatile than 1,8-dibromooctane in the temperature range covered (p_sat varies from 3 to 250 Pa and from 0.53 to 62 Pa, respectively) and is also approximately three times more soluble in water (mole fraction solubilities at 25 °C of 5.95 × 10⁻⁷ and 1.92 × 10⁻⁷, respectively). A combination of the two sets of data allowed the calculation of the Henry’s law constants and the air water partition coefficients. A simple group contribution concept was used to rationalize the data obtained.     

Arsenic in sediments from the southeastern Baltic Sea

Arsenic occurs as a persistent constituent in many of the chemical weapons dumped into the Baltic Sea; it can be used as an indicator of leakage and dispersal of released munitions to the marine environment. Total arsenic was analysed in sediment samples taken from the Lithuanian economic zone in the Baltic Sea, which included samples from the chemical munitions dumpsite in the Gotland Basin and national monitoring stations in the southeastern Baltic Sea. Arsenic concentrations in sediments ranged from 1.1 to 19.0 mg kg(-1), with an average of 3.4 mg kg(-1). Although there was evidence of slightly elevated arsenic content in sediments near the weapons dumpsite, arsenic concentrations were nevertheless quite low relative to other investigations in the Baltic and North Seas.     

Beyond depletion: Daily self-control motivation as an explanation of self-control failure at work

The organizational self-control literature usually applies resource perspectives that explain self-control failure at work by depletion of self-control resources. However, these perspectives neglect the role of self-control motivation. On a daily level, we examine several self-control aspects (resources, motivation, demands, and effort) as predictors of a manifestation of self-control failure at work, namely, daily counterproductive work behavior toward the organization (CWB-O). Additionally, we investigate self-control effort as a mechanism predicting the depletion of self-control resources throughout the day. We analyzed data from 155 employees in a 2-week diary study with 2 daily measurement points. Multilevel path modeling showed that self-control motivation and self-control demands, but not self-control resource depletion, predicted self-control effort. There was an indirect effect from self-control motivation on CWB-O via self-control effort but no indirect effect from self-control demands on self-control resource depletion throughout the day via self-control effort. Findings suggest that self-control motivation is a crucial factor explaining self-control failure at work and cast further doubt on the idea that exerted self-control effort is the only mechanism leading to self-control resource depletion.     

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.     

Avian and Mammalian Translocations: Update and Reanalysis of 1987 Survey Data

In 1993 we conducted a follow-up study of the 1987 survey by Griffith et al. (1989) of 421 avian and mammalian translocation programs in North America, Australia, and New Zealand to reassess the programs' status and the biological and methodological factors associated with success. Our survey response rate was 81%. Approximately 38% of usable programs in 1993 reported a change in outcome from 1987 (e.g., a translocated population was "declining" but now is "self-sustaining"), but the difference between the overall success rates was not statistically significant (66% in 1987 and 67% in 1993). Since 1987, an increase was observed in the median number of animals translocated per program (31.5 to 50.5), median duration of releases (2 to 3 years), and proportion of programs releasing more than 30 animals (46% to 68%). Multiple logistic regression analyses indicated that release into the core of the historical range, good-to-excellent habitat quality, native game species, greater numbers of released animals, and an omnivorous diet were positively associated with translocation success. Moreover, our results indicate that translocated birds were less successful at establishing self-sustaining populations than translocated mammals. Our findings, using comparable logistic analyses, generally corroborate the results of Grifftth et al. (1989). Variables not found to be significantly correlated with translocation success include species' reproductive potential (number of offspring and first age of reproduction), number and duration of the releases, and source of the translocated animals (wild-caught versus captive-reared).     

Hydrologic regime and herbivory stabilize an alternative state in Yellowstone National Park.

A decline in the stature and abundance of willows during the 20th century occurred throughout the northern range of Yellowstone National Park, where riparian woody-plant communities are key components in multiple-trophic-level interactions. The potential causes of willow decline include climate change, increased elk browsing coincident with the loss of an apex predator, the gray wolf, and an absence of habitat engineering by beavers. The goal of this study was to determine the spatial and temporal patterns of willow establishment through the 20th century and to identify causal processes. Sampled willows established from 1917 to 1999 and contained far fewer young individuals than was predicted from a modeled stable willow population, indicating reduced establishment during recent decades. Two hydrologically distinct willow establishment environments were identified: fine-grained beaver pond sediments and coarse-grained alluvium. Willows established on beaver pond sediment earlier in time, higher on floodplain surfaces, and farther from the current stream channel than did willows on alluvial sediment. Significant linear declines from the 1940s to the 1990s in alluvial willow establishment elevation and lateral distance from the stream channel resulted in a much reduced area of alluvial willow establishment. Willow establishment was not well correlated with climate-driven hydrologic variables, but the trends were consistent with the effects of stream channel incision initiated in ca. 1950, 20-30 years after beaver dam abandonment. Radiocarbon dates and floodplain stratigraphy indicate that stream incision of the present magnitude may be unprecedented in the past two millennia. We propose that hydrologic changes, stemming from competitive exclusion of beaver by elk overbrowsing, caused the landscape to transition from a historical beaver-pond and willow-mosaic state to its current alternative stable state where active beaver dams and many willow stands are absent. Because of hydrologic changes in streams, a rapid return to the historical state may not occur by reduction of elk browsing alone. Management intervention to restore the historical hydrologic regime may be necessary to recover willows and beavers across the landscape.     

On the integration of individual foraging strategies with colony ergonomics in social insects: nectar-collection in honeybees

Summary We experimentally tested whether foraging strategies of nectar-collecting workers of the honeybee (Apis mellifera) vary with colony state. In particular, we tested the prediction that bees from small, fast growing colonies should adopt higher workloads than those from large, mature colonies. Queenright small colonies were set up by assembling 10 000 worker bees with approximately 4100 brood cells. Queenright large colonies contained 35 000 bees and some 14 500 brood cells. Thus, treatments differed in colony size but not in worker/brood ratios. Differences in workload were tested in the context of single foraging cycles. Individuals could forage on a patch of artificial flowers offering given quantities and qualities of nectar rewards. Workers of small colonies took significantly less nectar in an average foraging excursion (small: 40.1 ± 1.1 SE flowers; large: 44.8 ± 1.1), but spent significantly more time handling a flower (small: 7.3 ± 0.4 s ; large: 5.8 ± 0.4 s). When the energy budgets for an average foraging trip were calculated, individuals from all colonies showed a behavior close to maximization of net energetic efficiency (i.e., the ratio of net energetic gains to energetic costs). However, bees from small colonies, while incurring only marginally smaller costs, gained less net energy per foraging trip than those from large colonies, primarily as a result of prolonged handling times. The differences between treatments were largest during the initial phases of the experimental period when also colony development was maximally different. Our results are at variance with simple models that assume natural selection to have shaped behavior in a single foraging trip only so as to maximize colony growth. Offprint requests to: P. Schmid-Hempel     

Ozon in Waldökosystemen aus atmosphärenchemischer und pflanzenphysiologischer Sicht

The trend of rising ozone concentrations in forest ecosystems and the phytotoxicity of ozone demand a realistic risk assessment according to an internationally accepted and flux-based quality standard. Ozone fluxes within the canopy are influenced by chemical gas-phase reactions with nitrogen oxide and biogenic hydrocarbons and by surface deposition processes. Therefore, a differentiation of the ozone flux within the canopy is needed between stomatal uptake and other transport pathways. The Eddy Covariance technique is the method of choice for the determination of trace gas fluxes relevant for ozone chemistry. This method is also used for stomatal conductance measurements based on evapotranspiration fluxes and for emission measurements of biogenic hydrocarbons by PTR-MS. Although considerably research efforts were directed to canopy measurements in recent years, the underlying processes are not fully understood yet. Thus, major differences occur in the ratios of stomatal ozone uptake, non-stomatal deposition and gas-phase chemistry between different studies. Furthermore, the vertical concentration gradients within the canopy measured at several forest sites are rather inconsistent and the existing deposition models do rarely account for chemical transformation and detoxification processes. Only a simultaneous measurement of all photochemically relevant trace gases, plant physiological parameters at different sites and forest species over entire vegetation periods, and model parameterization according to the measurement results from the experimental sites will contribute to the clarification of the canopy processes and will ensure realistic risk assessments.     

Life cycle of the rhizostome jellyfish <Emphasis Type="Italic">Rhizostoma octopus</Emphasis> (L.) (Scyphozoa,Rhizostomeae), with studies on cnidocysts and statoliths

Stages in the life cycle of the rhizostome jellyfish Rhizostoma octopus (L.) were reared in the laboratory from planula to young medusa and are described here. Fertilization of eggs was external, and planulae, 110–150 μm in length, appeared after 2 days. These settled and developed into the scyphistoma stage. Scyphistomae reached a maximum size of 2.3 mm, bore up to 24 tentacles, and had a large manubrium. Polyps reproduced asexually mainly by podocysts. Strobilation was induced by temperature change. Each strobila released up to five ephyrae that measured 2.7–5.8 mm in diameter at liberation. During transformation from newly released ephyra to young medusa, velar lappets appeared and increased in number, the manubrium developed eight branched oral arms with epaulettes, and a marginal gastric network arose. Only one cnidocyst type, the “a”-atrichous haploneme, was present in the planula. In addition to these haplonemes, heterotrichous microbasic euryteles were observed in polyps, ephyrae, and medusae. Statoliths, located in the rhopalia, had a characteristic compact shape. These sensory structures increased in number and size with the growth of ephyrae and medusae.