Changes in redox states of respiratory pigments recorded from the eyes of live blowflies exposed to light stimuli and hypoxia

Time courses of mitochondrial responses to illumination-induced physiological loads and to hypoxia, were recorded optically from eyes of blowflies Calliphora vicina chalky. We isolated changes in redox states of haems a₃, a, c, and b. Two types of responses to light stimulation were observed. Haems b and a₃ responded with transient oxidation and haems a and c with reduction. The same two groups emerged in response to anoxic exposure. The onset of reduction of haems a and c had virtually no latency, while haems a₃ and b exhibited a transient oxidation followed by reduction only after 10–20 s. The dependence of the steady-state reduction level on P_\textO2 P_{{{\text{O}}_{2} }} produced the same groups. Haems a and c were significantly reduced at P_\textO2 P_{{{\text{O}}_{2} }} levels around 10 kPa while with haems b and a₃ load-induced oxidation was only replaced by reduction below 2 kPa. We propose haems respond to physiological loads in accordance with their steady-state reduction, which in turn depends largely on barriers for electron transport imposed by the mitochondrial membrane potential. We also propose it may be possible to assess the values of tissue P_\textO2 P_{{{\text{O}}_{2} }} and O₂ consumption by monitoring haems that are highly oxidized at rest such as haem a.     

Pollen and gene flow in fragmented habitats

Abstract. Habitat fragmentation affects both plants and pollinators. Habitat fragmentation leads to changes in species richness, population number and size, density, and shape, thus to changes in the spatial arrangement of flowers. These changes influence the amount of food for flower-visiting insects and the quantity and quality of pollinations. Seed set in small populations is often reduced and genetic variation is expected but not always found to be low. The majority of studies show that low flower densities have reduced pollination success and higher inbreeding. Density effects are stronger than size effects. Most studies concluded that species richness in flower-visiting insects is directly related to richness in plant species. However, the consequences of low insect species richness for pollination are not always clear, depending on the studied pollinator-plant relationship. The effects of the presence of simultaneously flowering species are highly dependent on the circumstances and may range from competition to facilitation. Other flowering plant species may play a role as stepping stones or corridor in the connection between populations. In the absence of stepping stones even short distances between populations act as strong barriers for gene flow. We illustrate the present review paper with own data collected for three plant species, rare in The Netherlands: Phyteuma spicatum ssp. nigrum (Campanulaceae), Salvia pratensis (Labiatae) and Scabiosa columbaria (Dipsacaceae). The species differ in their breeding systems and in the assemblage of visitor species. Data are shown on the effects of population size on species richness with consequences for seed set. Effects of flower density and isolation on pollen exchange are given. Since plant reproduction depends on the behaviour of individual insects and not on the overall behaviour of the species, the examples all point to individual insects and extrapolate to effects at the species level.     

Oceanographic Conditions Limit the Spread of a Marine Invader along Southern African Shores

Invasive species can affect the function and structure of natural ecological communities, hence understanding and predicting their potential for spreading is a major ecological challenge. Once established in a new region, the spread of invasive species is largely controlled by their dispersal capacity, local environmental conditions and species interactions. The mussel Mytilus galloprovincialis is native to the Mediterranean and is the most successful marine invader in southern Africa. Its distribution there has expanded rapidly and extensively since the 1970s, however, over the last decade its spread has ceased. In this study, we coupled broad scale field surveys, Ecological Niche Modelling (ENM) and Lagrangian Particle Simulations (LPS) to assess the current invaded distribution of M. galloprovincialis in southern Africa and to evaluate what prevents further spread of this species. Results showed that all environmentally suitable habitats in southern Africa have been occupied by the species. This includes rocky shores between Rocky Point in Namibia and East London in South Africa (approx. 2800 km) and these limits coincide with the steep transitions between cool-temperate and subtropical-warmer climates, on both west and southeast African coasts. On the west coast, simulations of drifting larvae almost entirely followed the northward and offshore direction of the Benguela current, creating a clear dispersal barrier by advecting larvae away from the coast. On the southeast coast, nearshore currents give larvae the potential to move eastwards, against the prevalent Agulhas current and beyond the present distributional limit, however environmental conditions prevent the establishment of the species. The transition between the cooler and warmer water regimes is therefore the main factor limiting the northern spread on the southeast coast; however, biotic interactions with native fauna may also play an important role.     

Ten years of life in compost: temporal and spatial variation of North German Caenorhabditis elegans populations

The nematode Caenorhabditis elegans is a central laboratory model system in almost all biological disciplines, yet its natural life history and population biology are largely unexplored. Such information is essential for in‐depth understanding of the nematode's biology because its natural ecology provides the context, in which its traits and the underlying molecular mechanisms evolved. We characterized natural phenotypic and genetic variation among North German C. elegans isolates. We used the unique opportunity to compare samples collected 10 years apart from the same compost heap and additionally included recent samples for this and a second site, collected across a 1.5‐year period. Our analysis revealed significant population genetic differentiation between locations, across the 10‐year time period, but for only one location a trend across the shorter time frame. Significant variation was similarly found for phenotypic traits of likely importance in nature, such as choice behavior and population growth in the presence of pathogens or naturally associated bacteria. Phenotypic variation was significantly influenced by C. elegans genotype, time of isolation, and sampling site. The here studied C. elegans isolates may provide a valuable, genetically variable resource for future dissection of naturally relevant gene functions.     

Novel reversible methionine aminopeptidase-2 (MetAP-2) inhibitors based on purine and related bicyclic templates

The natural product fumagillin 1 and derivatives like TNP-470 2 or beloranib 3 bind to methionine aminopeptidase 2 (MetAP-2) irreversibly. This enzyme is critical for protein maturation and plays a key role in angiogenesis. In this paper we describe the synthesis, MetAP-2 binding affinity and structural analysis of reversible MetAP-2 inhibitors. Optimization of enzymatic activity of screening hit 10 (IC₅₀: 1 μM) led to the most potent compound 27 (IC₅₀: 0.038 μM), with a concomitant improvement in LLE from 2.1 to 4.2. Structural analysis of these MetAP-2 inhibitors revealed an unprecedented conformation of the His339 side-chain imidazole ring being co-planar sandwiched between the imidazole of His331 and the aryl-ether moiety, which is bound to the purine scaffold. Systematic alteration and reduction of H-bonding capability of this metal binding moiety induced an unexpected 180° flip for the triazolo[1,5-a]pyrimdine bicyclic template.     

Sex determination of the Early Cretaceous clam shrimp Eosestheria middendorfii (Yixian Formation,China)

Clam shrimps have been recognized as a key group for the study of reproductive system evolution, owing to the diversity of sexual systems in extant members. However, there are comparatively little data on fossil taxa. In this study, we reveal the sexual system of the Early Cretaceous clam shrimp Eosestheria middendorfii (Yixian Formation, China). This is the first study that restricts the analysis to a single cohort, minimizing the otherwise considerable impact of ecophenotypic variation within this species. In addition, the presence of egg clutches, which identifies some individuals as either female or hermaphroditic, serves as an independent indicator for sex prior to the statistical treatment of the data. Obligate sexuality (‘dioecy’) is the inferred reproductive system for E. middendorfii and sexual dimorphism accounts for about 10% of the adult shape variation. Carapace shape variation resulting from malformation and deformation is more pronounced than the underlying sexual dimorphism. Subtle sexual dimorphism, smaller and slightly more elongate females, lateral egg clutches, and egg diameters of about 140 μm indicate that E. middendorfii is closely allied with the extant family Cyzicidae.