Variability of tropospheric hydroperoxides at a coastal surface site in Antarctica

The annual cycles of hydrogen peroxide (H₂O₂) and methylhydroperoxide (MHP) have been investigated at a remote site in Antarctica in order to study seasonal variations as well as chemical processes in the troposphere. The measurements have been performed from March 1997 to January 1998 and in February 1999 at the German Antarctic research station Neumayer which is located at 70°39′S, 8°15′W. The obtained time series for hydrogen peroxide and methylhydroperoxide in near-surface air represents the first all-year measurements in Antarctica and indicates clearly the occurrence of seasonal variations. During polar night mean values of 0.054±0.046 ppbv (range<0.03–0.11 ppbv) for hydrogen peroxide and 0.089±0.052 ppbv (range<0.05–0.14 ppbv) for methylhydroperoxide were detected. At the sunlit period higher Mixing ratios were found, 0.20±0.13 ppbv (range<0.03–0.91 ppbv) for hydrogen peroxide and 0.19±0.10 ppbv (range<0.05–0.89 ppbv) for methylhydroperoxide. Occasional long-range transport of air masses from mid-latitudes caused enhanced peroxide concentrations at polar night. During the period of stratospheric ozone depletion we observed peroxide mixing ratios comparable to typical winter levels.     

Linking ground-water age and chemistry data along flow paths: implications for trends and transformations of nitrate and pesticides

Tracer-based ground-water ages, along with the concentrations of pesticides, nitrogen species, and other redox-active constituents, were used to evaluate the trends and transformations of agricultural chemicals along flow paths in diverse hydrogeologic settings. A range of conditions affecting the transformation of nitrate and pesticides (e.g., thickness of unsaturated zone, redox conditions) was examined at study sites in Georgia, North Carolina, Wisconsin, and California. Deethylatrazine (DEA), a transformation product of atrazine, was typically present at concentrations higher than those of atrazine at study sites with thick unsaturated zones but not at sites with thin unsaturated zones. Furthermore, the fraction of atrazine plus DEA that was present as DEA did not increase as a function of ground-water age. These findings suggest that atrazine degradation occurs primarily in the unsaturated zone with little or no degradation in the saturated zone. Similar observations were also made for metolachlor and alachlor. The fraction of the initial nitrate concentration found as excess N2 (N2 derived from denitrification) increased with ground-water age only at the North Carolina site, where oxic conditions were generally limited to the top 5 m of saturated thickness. Historical trends in fluxes to ground water were evaluated by relating the times of recharge of ground-water samples, estimated using chlorofluorocarbon concentrations, with concentrations of the parent compound at the time of recharge, estimated by summing the molar concentrations of the parent compound and its transformation products in the age-dated sample. Using this approach, nitrate concentrations were estimated to have increased markedly from 1960 to the present at all study sites. Trends in concentrations of atrazine, metolachlor, alachlor, and their degradates were related to the timing of introduction and use of these compounds. Degradates, and to a lesser extent parent compounds, were detected in ground water dating back to the time these compounds were introduced.     

Choosy males from the underground: male mating preferences in surface- and cave-dwelling Atlantic mollies (Poecilia mexicana)

Atlantic mollies (Poecilia mexicana) inhabit a variety of surface habitats, but they also occur in a sulfur cave in southern Mexico. We examined male mate choice relative to female body size in the cave population and in the most closely related surface-dwelling population from a nearby river. Males from both populations were either light- or dark-reared and could choose between two differently sized females either on the basis of visual cues in light or on the basis of solely nonvisual cues in darkness. Sexual preferences were estimated from the degree of association. Cave molly males always showed a preference for the larger female, both in light and in darkness. Among the surface males, only light-reared males showed a preference in the visual cues test, but not in darkness. In a control experiment, we demonstrated that male association preferences directly translate into actual mating preferences. Apparently, using visual cues for mate choice is the ancestral state in this system, and using nonvisual cues has evolved as a novel trait in the cave population. We discuss the evolution of nonvisual male mate choice in the context of changed environmental conditions, namely the absence of light, hypoxia, and toxic hydrogen sulfide in the cave.     

Linkage of biomarkers along levels of biological complexity in juvenile and adult diazinon fed terrestrial isopod (Porcellio scaber, Isopoda, Crustacea)

In parallel laboratory experiments, we determined the effect of a typical representative of organophosphorous pesticides, diazinon, on AChE activity, lipid, protein and glycogen content, weight change, feeding activity and mortality of juvenile and adult terrestrial isopods Porcellio scaber (Isopoda, Crustacea). Organophosphorous pesticides (OP) are among the most extensively used pesticides, which have replaced organochlorine pesticides. OPs inhibit the enzyme acetylcholinesterase (AChE), resulting in neurotoxicity. They have more widespread effects on non-target organisms than do organochlorine pesticides. The aim of this study was to link effect of diazinon on target enzyme to energy reserves and to integrated biomarker responses in juvenile and adult P. scaber. The non-observed effect concentration (NOEC) for AChE activity after diazinon exposure in two weeks toxicity study with isopods was below 5 microg/g diazinon. There was a good agreement between concentrations at which AChE and survival were affected (10 microg/g diazinon in juveniles, 100 microg/g diazinon in adults). We revealed a link among AChE activity, protein content and mortality. Glycogen and lipid content, feeding activity and weight change were not affected in two weeks diazinon exposure up to 100 microg/g diazinon. Juveniles were affected at concentrations that were an order of magnitude lower than those provoking similar effects on adults. Recommendations are made for future toxicity studies with terrestrial isopods.     

Öko-Audit eines Bio-Agrar-Betriebes

Environmental impacts of a farm which is managed in accordance with ecological criteria is assessed. To this end the ecoaudit ordinance of the European Union 1836/93/EWG is used as guiding principle. This article focuses on methods and results of the impact assessment (chapter 2, 3) and the recommendations derived from that (chapter 4). Before that, objectives of investigation (chapter 1.1), key topics of the assessment ordinance are summarised (chapter 1.2), and finally the farm and the main fields of investigation are described (chapter 1.3). The density of complex hedge rows, as one from 21 assessment criteria, exceeds the limit of tolerance. The investigation underlines the need for further methodological harmonisation.     

Do dominants have higher heterozygosity? Social status and genetic variation in brown trout, Salmo trutta

A key question of evolutionary importance is what factors influence who becomes dominant. Individual genetic variation has been found to be associated with several fitness traits, including behaviour. Could it also be a factor influencing social dominance? We investigated the association between social status and the amount of intra-individual genetic variation in juvenile brown trout (Salmo trutta). Genetic variation was estimated using 12 microsatellite loci. Dominant individuals had higher mean heterozygosity than subordinates in populations with the longest hatchery background. Heterozygosity–heterozygosity correlations did not find any evidence of inbreeding; however, single-locus analysis revealed four loci that each individually differed significantly between dominant and subordinate fish, thus giving more support to local than general effect as the mechanism behind the observed association between genetic diversity and a fitness-associated trait. We did not find any significant relation between mean d ² and social status, or internal relatedness and social status. Our results suggest that individual genetic variation can influence dominance relations, but manifestation of this phenomenon may depend on the genetic background of the population.     

Cave molly females (Poecilia mexicana, Poeciliidae, Teleostei) like well-fed males

We examined the preference of Atlantic molly females (Poecilia mexicana) to associate with a well-fed or a starved male in simultaneous choice tests. Females from three different populations were tested in three treatments: (1) the females could choose on the basis of multiple cues from the males (visual plus non-visual); (2) only non-visual cues could be perceived in darkness, (3) only visual cues were presented. The three tested populations differ clearly in their ecology: one population occurs in a typical river habitat, the second one in a milky sulfur creek outside a cave, and the third population occurs in a cave habitat (cave molly). In the river-dwelling population, females never showed a preference. In the population from the sulfur creek, females preferred to associate with the well-nourished male when visual cues from the males were available. Only cave molly females exhibited a strong preference for well-nourished males in all treatments. A morphological comparison demonstrated that wild-caught males from river habitats are typically in a good nutritional state. In the sulfur creek, males showed signs of starvation. Cave molly males were in an even worse nutritional state. In the cave population, saturated males probably indicate high fitness, thereby driving the evolution of the preference for good male nutritional state.Communicated by K. Lindström     

A genetic component to size in queens of the ant,<Emphasis Type="Italic"> Formica truncorum</Emphasis>

The genetic basis of morphological traits in social insects remains largely unexplored. This is even true for individual body size, a key life-history trait. In the social insects, the size of reproductive individuals affects dispersal decisions, so that small size in queens is often associated with reduced dispersal, and large size with long-range dispersal and independent colony founding. Worker size is connected to division of labour when workers specialize in certain tasks according to their size. In many species, variation in worker size has been shown to increase colony performance. In this study, we present the first evidence of an additive genetic component to queen size in ants, using maternal half sib analysis. We also compared intra-colony size variation in colonies with high (queen doubly mated) versus low (queen singly mated) genetic variability. We found a high and significant heritability (h²=0.51) for queen size in one of the two study years, but not in the other. Size variation among queens was greater in colonies headed by a doubly mated queen in one of the study years, but not in the other. This indicates that genetic factors can influence queen size, but that environmental factors may override these under some circumstances. The heritability for worker size was low (h²=0.09) and non-significant. Increased genetic diversity did not increase worker size variation in the colonies. Worker size appeared largely environmentally determined, potentially allowing colonies to adjust worker size ratios to current conditions.Communicated by J. Heinze     

Identification of sperm proteins as candidate biomarkers for the analysis of reproductive isolation in Mytilus: a case study for the enkurin locus

Sperm proteins of the marine sessile mussels of the Mytilus edulis species complex are models to investigate reproductive isolation and speciation. This study aimed at identifying sperm proteins and their corresponding genes. This was aided by the use of monoclonal antibodies that preferentially bind to yet unknown sperm molecules. By identifying their target molecules, this approach identified proteins with relevance to Mytilus sperm function. This procedure identified 16 proteins, for example, enkurin, laminin, porin and heat shock proteins. The potential use of these proteins as genetic markers to study reproductive isolation is exemplified by analysing the enkurin locus. Enkurin evolution is driven by purifying selection, the locus displays high levels of intraspecific variation and species-specific alleles group in distinct phylogenetic clusters. These findings characterize enkurin as informative candidate biomarker for analyses of clinal variation and differential introgression in hybrid zones, for example, to understand determinants of reproductive isolation in Baltic Mytilus populations.