Speciation and carcinogenic classification—some limits of assessment and prevention procedures—the case of “nickel”

The speciation of nickel is of the highest importance for the definition of lists of substances for regulatory activity in terms of prevention, regarding possible cancer risk. A review is made of the different attitudes of outstanding administrations in front of nickel speciation. Some of them show a maximum of care in chemical definition, others reflect a lack of scientific rigor leading to generic classifications, more or less abusive. The great complexity of the chemistry and physicochemistry of nickel imposes the “two‐level speciation concept” (chemical and physicochemical), at least for compliance with the “Good Laboratory Practice” as far as experimental toxicology is concerned. Recommendations are exposed for the attention of toxicologists and regulators who have been for some years now extremely solicited for prevention aims.     

Elucidating the function of ejaculate expulsion and consumption after copulation by female Euxesta bilimeki

Postcopulatory processes can influence male reproductive success in several animal species. Females can use different mechanisms to bias male paternity after copulation. One of such mechanisms consists in expelling all or part of the ejaculate after copulation. Euxesta bilimeki is an Ulidiid fly whose females not only frequently expel ejaculates after mating but also consume the ejaculate after expulsion. In order to understand the significance of these behaviors we examined video recordings of courtship, copulatory, and postcopulatory behaviours. The presence of sperm in female storage organs was confirmed after mating with males of different sizes and was correlated with duration of courtship, copulation, and the period from the end of copulation to ejaculate expulsion. The effect of ejaculate consumption on female fitness (fecundity and longevity) was compared among females held under different dietary treatments: a rich diet consisting of protein, sugar and water, an intermediate diet composed of sugar and water, a poor diet of only water and females that were completely deprived of food and water. All of the observed females expelled ejaculates after mating. The probability of storing sperm in the two spermathecae and the ventral receptacle was correlated with interactions between the duration of all behaviours examined and male size. Except for starved females, who lived longer when allowed to consume ejaculates, ejaculate consumption had no effect on fitness. Results suggest that females can bias sperm storage according to male mating effort, while the consumed ejaculate had some nutritional value only evident when females were completely starved.     

The role of Greenland sharks (Somniosus microcephalus) in an Arctic ecosystem: assessed via stable isotopes and fatty acids

The Greenland shark (Somniosus microcephalus) is the only shark species known to inhabit ice-covered seas in the North Atlantic, but remains a missing component in most studies of Arctic food webs. In the present study, stable isotopes (SIs) of nitrogen (δ¹⁵N) and carbon (δ¹³C) and fatty acids (FAs) were analyzed to identify the role of Greenland sharks (sampled during June 2008–2009) in Kongsfjorden, a productive fjord on the west coast of Svalbard, Norway (~79ºN, 12–13ºE). The Greenland shark fed at a high trophic position (4.8) based on δ¹⁵N values, and δ¹³C confirmed that most (70 %) of their carbon was derived from phytoplankton-based food chains, which is consistent with a heavy reliance on pelagic teleosts and seals. Greenland sharks from Kongsfjorden had fatty acid profiles in both muscle and plasma (e.g., low 20:1n-9, high 22:5n-3) that suggested a low portion of Greenland halibut (Reinhardtius hippoglossoides) and high proportion of gadoids and seals in their diet compared to Greenland sharks sampled in Cumberland Sound, Canada, during April 2008, which were previously shown to derive much of their energy from Greenland halibut. The high proportions of seal fatty acids in both slow- (muscle) and fast- (plasma) turnover tissues indicate that trophic interactions between Greenland sharks and seals in Kongsfjorden are a common occurrence. Results from the present study suggest that Greenland sharks likely play a unique and significant role in Arctic marine food webs as a top predator of fishes and marine mammals.     

Vertical infiltration of fuel oil hydrocarbons in an agricultural soil

The influence of rainfall, air temperature and soil moisture on the vertical mobility in the soil of fuel oil hydrocarbons (HC) was investigated in a field experiment. A controlled spreading of fuel oil (nC10‐nC25) was performed at a rate of 5 L HCm^‐2 on an agricultural soil in summer and in winter. Concentration, chemical composition of HC and soil moisture were regularly determined at different soil depths between 0 and 140 cm, 1 h, 3, 8and 15 days (d) after the spreading of oil. Sorption of hydrocarbons onto the organo‐mineral matrix of the soil was studied in laboratory experiments. The results showed that in summer, with an air temperature of 24°C and without water leaching in the soil profile, 65% of the initial HC remained trapped in the 0–140 cm soil layer, about 20% of the HC volatilized and around 15% migrated deeper. A vertical selective migration of the lightest (nC10‐nC15) HC (naphthas) was shown lSd after the spreading of fuel oil. Naphthas progressively reached the 120–140 cm soil layers whereas the heavy fractions of oil (nC17‐nC25) migrated and concentrated in the 0–60 cm soil layers. In winter, when soil was regularly watered by rainfalls and at low air temperatures, only 47% of the initial HC remained in the 0–140 cm profile after 15 d. A fast vertical infiltration of naphthas occurred within the first 3 d. After 15 d, all HC were detected in the same relative amounts as in the initial oil in the whole profile. Volatilization was negligible in winter and an increase in the migration of total oil at depth in the soil profile was shown. As inferred from the laboratory experiments, the high soil moisture led to the decrease in HC sorption on the organo‐mineral matter of the soil.     

Determining patterns of variability in ecological communities: time lag analysis revisited

All ecological communities experience change over time. One method to quantify temporal variation in the patterns of relative abundance of communities is time lag analysis (TLA). It uses a distance-based approach to study temporal community dynamics by regressing community dissimilarity over increasing time lags (one-unit lags, two-unit lags, three-unit lags). Here, we suggest some modifications to the method and revaluate its potential for detecting patterns of community change. We apply Hellinger distance based TLA to artificial data simulating communities with different levels of directional and stochastic dynamics and analyse their effects on the slope and its statistical significance. We conclude that statistical significance of the TLA slope (obtained by a Monte Carlo permutation procedure) is a valid criterion to discriminate between (i) communities with directional change in species composition, regardless whether it is caused by directional abundance change of the species or by stochastic change according to a Markov process, and (ii) communities that are composed of species with population sizes oscillating around a constant mean or communities whose species abundances are governed by a white noise process. TLA slopes range between 0.02 and 0.25, depending on the proportions of species with different dynamics; higher proportions of species with constant means imply shallower slopes; and higher proportions of species with stochastic dynamics or directional change imply steeper slopes. These values are broadly in line with TLA slopes from real world data. Caution must be exercised when TLA is used for the comparison of community time series with different lengths since the slope depends on time series length and tends to decrease non-linearly with it.     

Differing patterns of sequestration of iridoid glycosides in the Mecininae (Coleoptera, Curculionidae)

We analyzed several species of the weevil family Mecininae (Coleoptera, Curculionidae) that all feed on iridoid glycoside (IG) containing plants of the Plantaginaceae to investigate whether the beetles sequester these deterrent substances from their host plants. Within the Mecininae two genera of the tribe Cionini were found to sequester aucubin and catalpol: Cionus Clairville and Schellenberg and Cleopus Dejean. Both analyzed genera of the Mecinini, Mecinus Germar and Rhinusa Stephens, do not sequester IGs although the compounds are present in their food plants. They thus represent the first case of specialists on IG plants that have not evolved adaptations to use the compounds. However, in contrast to the Cionini these genera have a hidden lifestyle, so that their need for defence might be lower. Both Cionus and Cleopus, sequester catalpol with a higher efficiency than aucubin. However, in contrast to Cionus species, Cleopus species only sequester catalpol. In species feeding on Scrophularia, the aucubin concentration is higher while in beetles on Verbascum catalpol is usually dominating. This pattern can also be detected in the only species living on both plants, Cionus hortulanus. The ability to sequester IGs must have a single origin at the base of the sister genera Cionus and Cleopus.     

Factors driving mortality and growth at treeline: a 30-year experiment of 92 000 conifers

Understanding the interplay between environmental factors contributing to treeline formation and how these factors influence different life stages remains a major research challenge. We used an afforestation experiment including 92 000 trees to investigate the spatial and temporal dynamics of tree mortality and growth at treeline in the Swiss Alps. Seedlings of three high-elevation conifer species (Larix decidua, Pinus mugo ssp. uncinata, and Pinus cembra) were systematically planted along an altitudinal gradient at and above the current treeline (2075 to 2230 m above sea level [a.s.l.]) in 1975 and closely monitored during the following 30 years. We used decision-tree models and generalized additive models to identify patterns in mortality and growth along gradients in elevation, snow duration, wind speed, and solar radiation, and to quantify interactions between the different variables. For all three species, snowmelt date was always the most important environmental factor influencing mortality, and elevation was always the most important factor for growth over the entire period studied. Individuals of all species survived at the highest point of the afforestation for more than 30 years, although mortality was greater above 2160 m a.s.l., 50-100 m above the current treeline. Optimal conditions for height growth differed from those for survival in all three species: early snowmelt (ca. day of year 125-140 [where day 1 is 1 January]) yielded lowest mortality rates, but relatively later snowmelt (ca. day 145-150) yielded highest growth rates. Although snowmelt and elevation were important throughout all life stages of the trees, the importance of radiation decreased over time and that of wind speed increased. Our findings provide experimental evidence that tree survival and height growth require different environmental conditions and that even small changes in the duration of snow cover, in addition to changes in temperature, can strongly impact tree survival and growth patterns at treeline. Further, our results show that the relative importance of different environmental variables for tree seedlings changes during the juvenile phase as they grow taller.     

Insights on plant interaction between dominating species from patterns of plant association: expected covariance of pin-point cover measurements of two species

It has been suggested that in order to infer ecological processes from observed patterns of species abundance we need to investigate the covariance in species abundance. Consequently, an expression for the expected covariance of pin-point cover measurements of two species is developed. By comparing the observed covariance with the expected covariance we get a new type of information on the spatial arrangement of two species. Here the discrepancy between the observed and expected covariance may be thought of as a measure of the spatial configuration of the two species that may indicate underling ecological processes. The method is applied in a case study of Calluna vulgaris and Deschampsia flexuosa on dry heathland sites. The observed covariance of Calluna and Deschampsia at the level of the sites was positively and significantly correlated with the expected covariance. Negative covariance was observed on sites where both Calluna and Deschampsia had a high cover, which is in agreement with the notion that both species form distinct patches. Oppositely, at sites where both species have a low cover, we found that both the expected and observed covariance were positive. The proposed measure for the expected covariance of two species does capture information on the combined spatial configuration of the two species if the species are common. We show how this may be relevant for understanding the underlying ecological processes leading to the observed covariance.     

Refueling while flying: foraging bats combust food rapidly and directly to power flight

Flying vertebrates, such as bats, face exceptionally high energy costs during active flapping flight. Once airborne, energy turnover may exceed basal metabolic rate by a factor of up to 15. Here, we asked whether fuel that powers flight originates from exogenous (dietary nutrients), endogenous sources (mostly body lipids or glycogen), or a combination of both. Since most insectivorous bats fly continuously over relatively long time periods during foraging, we assumed that slowly mobilized glycogen, although suitable for supporting brief sallying flights, is inadequate to power aerial insect-hunting of bats. We hypothesized that the insect-feeding Noctilio albiventris rapidly mobilizes and combusts nutrients from insects it has just eaten instead of utilizing endogenous lipids. We used the stable carbon isotope ratio in the bats' exhaled breath (delta13C(brth)) to assess the origin of metabolized substrates of resting and flying N. albiventris in two nutritional conditions: fasted and recently fed. The breath of fasted resting bats was depleted in 13C in relation to their insect diet (delta13C(diet)), indicating the combustion of 13C depleted body lipids. In contrast to this, delta13C(brth) of bats that had recently fed closely matched delta13C(diet) in both resting and flying bats, suggesting a quick mobilization of ingested nutrients for metabolism. In contrast to most non-volant mammals, bats have evolved the ability to fuel their high energy expenditure rates through the rapid combustion of exogenous nutrients, enabling them to conquer the nocturnal niche of aerial insectivory.     

Beurteilung des Ozonrisikos für die Waldregionen Bayerns am Beispiel des Jahres 2002 und des Extremtrockenjahres 2003 auf der Basis der externen Ozonexposition und der internen Ozonaufnahme

Background, aim, and scope Increasing background concentrations of ground-level tropospheric ozone and more frequent and prolonged summer drought incidences due to climate change are supposed to increase the stress on Bavarian forests. For such scenarios growth reduction and yield losses are predicted. Sustainable forest management in Bavaria aims to significantly increase the proportion of beech (Fagus sylvatica L.) because of its broad ecological amplitude. In our regional study different approaches for calculating ozone impact were used to estimate the risks for Bavarian forests in the average climatic, rather moist year 2002 and the extremely dry year 2003.Materials and methods Measurements were conducted for eleven forest ecosystem sites and two forest research sites representing typical Bavarian forest stands under different climatic conditions and situated in different altitudes. For risk assessment currently used approaches were applied either based on the calculation of the cumulative ozone exposure (external dose; MPOC maximal permitted ozone concentration; critical level AOT40_phen? accumulated ozone exposure over a threshold of 40 nl [O₃] l^–1, for the effective phenolgy of beech) or based on the calculation of the phytomedically relevant ozone flux into the stomata (internal dose, critical level AF_st>1,6, accumulated stomatal flux above a flux threshold of 1.6 nmol O₃?m^–2 PLA; PLA = projected leaf area). For calculations continuously recorded ozone concentrations and meteorological and phenological data from nearby rural open field background measuring stations from the national air pollution control and from forested sites were used. Additionally ozone induced leaf symptoms were assessed.Results The exposure-based indices AOT40_phen and MPOC as well as the flux-based index AF_st>1.6suggest that Bavarian forests are at risk from O₃ during a rather moist average year concerning climate conditions (2002) as well as in an extreme dry year (2003). Thus, growth reductions of 5?% are predicted when thresholds are exceeded. Threshold exceedance occurred in both years at all plots, mostly already at the beginning of the growing season and often even many times over. Ozone induced leaf symptoms could be detected only on a few plots in a very slight occurrence.Discussion The results for the applied critical level indices differed depending on climatic conditions during the growing seasons: Regarding exposure-based indices, the highest degree of threshold exceedance occurred in the dry year of 2003 at all plots; the flux-based approach indicated the highest stomatal ozone uptake and thus an increased risk at moist sites or during humid years, whereas the risk was decreasing at dry sites with prolonged water limitation. Hence, soil and accordingly plant water availability was the decisive factor for the flux-modelled internal ozone uptake via stomata. Drought and increased ozone impact can generate synergistic, but also antagonistic effects for forest trees. At water limited rather dry forest sites restricted transpiration and thus production, but concurrently lower ozone uptake and reduced risk for damage can be expected.Conclusions, recommendations, and perspectives For realistic site-specific risk assessment in forest stands the determination of the internal ozone dose via modeling flux based internal stomatal ozone uptake is more appropriate than the calculation of the external ozone dose. The predicted 5?% growth reductions are in discrepancy with the frequently observed increment increase during the last decades in forest stands. Comprehensive and significant statistical verification for ozone induced forest growth reduction as well as the systematic validation of thresholds for ozone in the field is still lacking. However, a multiplicity of different specific new and retrospective growth analysis data should allow closing the gap. Moreover, the determination of canopy transpiration with sap flow measurements is a novel approach to provide cause-effect related, site specific results for the effective internal ozone dose as well as for canopy water supply and consecutively for regional risk estimation. A further future objective is the refinement of O₃ flux modelling by further consideration of soil/water budget characteristics and the above mentioned improved estimations of crown and canopy transpiration. Further, the introduction of threshold ranges for forest trees in view of their specific regional climatic conditions and their validation in real forest stands is necessary for developing meaningful ozone risk predictions for forests.