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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 443 (2006), S. 407-407 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] An unsuspected attachment mechanism may help these huge spiders to avoid catastrophic falls. Spiders spin silk from specialized structures known as abdominal spinnerets — a defining feature of the creatures — and this is deployed to capture prey, protect themselves, reproduce and ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 85 (1998), S. 31-33 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 86 (1999), S. 552-555 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract  Two main types of joints occur in the damselfly wing: mobile and immobile. Some longitudinal veins (RP2–, RP3&4–, and MP–) are elastically joined with cross veins, whereas other longitudinal veins (IR1+, IR2+, MA+, CuA'+) are firmly joined with cross veins. In this study we mapped the distribution of serial elastic elements in the wing. The occurrence of resilin, a rubberlike protein, in mobile joints suggests that the automatic twisting mechanism of the leading edge by aerodynamic force works not by flexibility but by the elasticity of these joints. First, it should result in elastic energy storage in the distal areas of the wing. Second, serial elastic elements of wing presumably act as dampers of an aerodynamic force, which are responsible for gradual twisting of the leading edge.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1440-1703
    Keywords: ants ; Formica polyctena ; myrmecochory ; seed aggregation ; seed dispersal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: In a field dominated by Formica polyctena Foerst. ants, we examined the effect of seed aggregation on the seed-removal rates of two plant species: a large-seeded obligate myrmecochore Viola odorata L. and a small-seeded diplochore Chelidonium majus L., which was autochorous as well as myrmecochorous. The effect was statistically non-significant in V. odorata but significant in C. majus, with more closely aggregated seeds having higher removal rates. The large seeds of the obligate myrmecochore were more quickly discovered and repeatedly removed by ant workers than were the small seeds of the diplochore.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 223 (1995), S. 289-302 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Functional comparative morphology of predatory legs in five species of water bugs (Ilyocoris cimicoides, Nepa cinerea, Ranatra linearis, Notonecta glauca, and Gerris lacustris) has been investigatd adn the following peculiarities of leg design were revealed.1Subcoxal articulation may be monoaxial (G. lacustris, N. glauca), or, in contrast to walking leg type, biaxial (N. cinerea, R. linearis, I. cimicoides); the first axis is oriented along the coxa (torsion axis), the second one is perpendicular to the first (non-torsion axis).2In contrast to walking leg type, which is characterized by cross suspension of the axis of coxal rotation in thoracal skeleton, this axis in G. lacustris is placed vertically. Non-torsion coxal axis in R. linearis is oriented strongly transversal. This axis directs the leg strike forward.3Legs in the majority of species are planar: Torsion axes of the coxa, femur, and tibia are placed in the same plane. Axes of rotation of consequent joints in I. cimicoides are reciprocally sloped. Therefore, the end of the leg outlines the spiral trajectory, when all angles of joints are opening (closing). This is an adaptation for clinging to the stems of water plants.4Passive adduction of the femur in the trochanter-femoral joint in N. glauca allows it to go around protuberances of the body wall, when the leg is sliding along them; recurrent femur movement during releasing from the obstacele is active due to the rt.fe muscle.5Only R. linearis has predatory legs, which permit the high-speed pursuit of potential prey; other species realize this function using the swimming legs, whereas the forelegs are used for the manipulation movements.6Muscle arrangement in the prothorax of different species reflects both leg construction and constructional constraints of body design. Powerful flexor muscles (co1, co2, co3, co5, fl.ti, et.ti in R. linearis; fl.ta, fl.ti in N. glauca; fl.ti in I. cimicoides) have long tendons and short muscle bundles, which originate on the leg wall. As a result, the powerful force is developed along the muscle tendon.7Some features of the predatory leg are common for the species studies: elongation of coxae, thickening of femora, and increase of the degree of junction of tibia and tarsus. The muscles, which move the distal segment of the leg, are reinforced and the sclerite of the fl.ti tendon is enlarged. The joint angle of the distal segment is increased to 120°. © 1995 Wiley-Liss, Inc.
    Additional Material: 27 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 217 (1993), S. 129-136 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Central projections of lyriform organs and tactile hairs on the chelicerae of the wandering spider Cupiennius salei were traced using anterograde cobalt fills. Different fibers arising from both mechanoreceptor types arborize in the cheliceral ganglia, which are part of the tritocerebrum, and in sensory longitudinal tracts in the center of the suboesophageal nerve mass together with afferent fibers arising from mechanoreceptors on the walking legs and the pedipalps. This convergence of sensory projections in the sensory longitudinal tracts might provide the anatomical basis for the coordination of the movements of different extremities during prey capture and feeding. The findings also support the hypothesis that the tritocerebrum originally was a preoral ganglion in spiders. © 1993 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
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  • 7
    Publication Date: 2016-11-24
    Description: Carbon capture and storage is promoted as a mitigation method counteracting the increase of atmospheric CO2 levels. However, at this stage, environmental consequences of potential CO2 leakage from sub-seabed storage sites are still largely unknown. In a 3-month-long mesocosm experiment, this study assessed the impact of elevated pCO2 levels (1,500 to 24,400 µatm) on Cerastoderma edule dominated benthic communities from the Baltic Sea. Mortality of C. edule was significantly increased in the highest treatment (24,400 µatm) and exceeded 50%. Furthermore, mortality of small size classes (0-1 cm) was significantly increased in treatment levels ≥6,600 µatm. First signs of external shell dissolution became visible at ≥1,500 µatm, holes were observed at 〉6,600 µatm. C. edule body condition decreased significantly at all treatment levels (1,500-24,400 µatm). Dominant meiofauna taxa remained unaffected in abundance. Densities of calcifying meiofauna taxa (i.e. Gastropoda and Ostracoda) decreased in high CO2 treatments (〉6,600 µatm), while the non - calcifying Gastrotricha significantly increased in abundance at 24,400 µatm. In addition, microbial community composition was altered at the highest pCO2 level. We conclude that strong CO2 leakage can alter benthic infauna community composition at multiple trophic levels, likely due to high mortality of the dominant macrofauna species C. edule.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 8
    Publication Date: 2019-12-13
    Description: While burial diagenetic processes of tropical corals are well investigated, current knowledge about factors initiating early diagenesis remains fragmentary. In the present study, we focus on recent Porites microatolls, growing in the intertidal zone. This growth form represents a model organism for elevated sea surface temperatures (SSTs) and provides important but rare archives for changes close to the seawater/atmosphere interface with exceptional precision on sea level reconstruction. As other coral growth forms, microatolls are prone to the colonization by endolithic green algae. In this case, the algae can facilitate earliest diagenetic alteration of the coral skeleton. Algae metabolic activity not only results in secondary coral porosity due to boring activities, but may also initiate reprecipitation of secondary aragonite within coral pore space, a process not exclusively restricted to microatoll settings. In the samples of this initial study, we quantified a mass transfer from primary to secondary aragonite of around 4% within endolithic green algae bands. Using δ18O, δ13C, Sr/Ca, U/Ca, Mg/Ca, and Li/Mg systematics suggests that the secondary aragonite precipitation followed abiotic precipitation principles. According to their individual distribution coefficients, the different isotope and element ratios showed variable sensitivity to the presence of secondary aragonite in bulk samples, with implications for microatoll-based SST reconstructions. The secondary precipitates formed on an organic template, presumably originating from endolithic green algae activity. Based on laboratory experiments with the green algae Ostreobium quekettii, we propose a conceptual model that secondary aragonite formation is potentially accelerated by an active intracellular calcium transport through the algal thallus from the location of dissolution into coral pore spaces. The combined high-resolution imaging and geochemical approach applied in this study shows that endolithic algae can possibly act as a main driver for earliest diagenesis of coral aragonite starting already during a coral’s life span.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
    Publication Date: 2023-03-07
    Description: Brachiopods present a key fossil group for Phanerozoic palaeo-environmental and palaeo-oceanographical reconstructions, owing to their good preservation and abundance in the geological record. Yet to date, hardly any geochemical proxies have been calibrated in cultured brachiopods and only little is known on the mechanisms that control the incorporation of various key elements into brachiopod calcite. To evaluate the feasibility and robustness of multiple Element/Ca ratios as proxies in brachiopods, specifically Li/Ca, B/Ca, Na/Ca, Mg/Ca, Sr/Ca, Ba/Ca, as well as Li/Mg, we cultured Magellania venosa, Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years with closely monitored ambient conditions, carbonate system parameters and elemental composition of the culture medium. The experimental setup comprised of two control aquariums (pH0 = 8.0 and 8.15, T = 10 °C) and treatments where pCO2 − pH (pH1 = 7.6 and pH2 = 7.35), temperature (T = 16 °C) and chemical composition of the culture medium were manipulated. Our results indicate that the incorporation of Li and Mg is strongly influenced by temperature, growth effects as well as carbonate chemistry, complicating the use of Li/Ca, Mg/Ca and Li/Mg ratios as straightforward reliable proxies. Boron partitioning varied greatly between the treatments, however without a clear link to carbonate system parameters or other environmental factors. The partitioning of both Ba and Na varied between individuals, but was not systematically affected by changes in the ambient conditions. We highlight Sr as a potential proxy for DIC, based on a positive trend between Sr partitioning and carbonate chemistry in the culture medium. To explain the observed dependency and provide a quantitative framework for exploring elemental variations, we devise the first biomineralisation model for brachiopods, which results in a close agreement between modelled and measured Sr distribution coefficients. We propose that in order to sustain shell growth under increased DIC, a decreased influx of Ca2+ to the calcifying fluid is necessary, driving the preferential substitution of Sr2+ for Ca2+ in the crystal lattice. Finally, we conducted micro-computed tomography analyses of the shells grown in the different experimental treatments. We present pore space – punctae – content quantification that indicates that shells built under increased environmental stress, and in particular elevated temperature, contain relatively more pore space than calcite, suggesting this parameter as a potential novel proxy for physiological stress and even environmental conditions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
    Publication Date: 2012-07-01
    Description: Sulfate-reducing bacteria are known to mediate dolomite formation under hypersaline conditions, but details of the crystal nucleation process are still poorly constrained. Our laboratory study demonstrates for the first time that Desulfobulbus mediterraneus, a marine sulfate-reducing bacterium, mediates primary precipitation of Mg-rich dolomite under anoxic conditions in media replicating modern seawater chemistry at low temperature (21 °C). Precipitation of crystals was associated with extracellular polymeric substances in a monospecific biofilm, providing templates for nucleation by altering the molar Mg/Ca ratio. After initial nucleation of single nanospherulites (∼50 nm), growth was mediated by aggregation, resulting in spherulites of ∼2–3 μm in diameter. Nucleation led to differences in Mg/Ca ratios and δ44/40Ca values among the organic material (i.e., biofilm including cells and extracellular polymeric substances; 0.87 ± 0.01 [2 SD] and 0.48‰ ± 0.11‰ [2 SE], respectively), the crystals (1.02 ± 0.11 [2 SD] and
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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