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  • Springer  (189)
  • 2000-2004  (76)
  • 1970-1974  (85)
  • 1965-1969  (28)
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  • 1
    Digitale Medien
    Digitale Medien
    Interdemic variation in mixed-species association patterns: common diurnal primates of Kibale National Park, Uganda (2000)
    Springer
    Behavioral ecology and sociobiology 47 (2000), S. 129-139 
    Details
    ISSN: 1432-0762
    Schlagwort(e): Key words Polyspecific associations ; Group living ; Ecological constraints model ; Food availability ; Group size ; Social organization ; Cercopithecines ; Colobines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  We used interdemic variation in the tendency to form mixed-species groups to examine the costs and benefits of association among the primates of Kibale National Park, Uganda. A year-long survey of six sites revealed that the amount of time that the five common diurnal primates [red colobus (Procolobus tephrosceles), black-and-white colobus (Colobus guereza), redtail monkeys (Cercopithecus ascanius), blue monkeys (Cercopithecus mitis), and grey-cheeked mangabeys (Lophocebus albigena)] spent in mixed-species groups varied dramatically among sites. In many cases, the proportion of time that species associated was positively related to their densities. By using detailed behavioral observations of redtail monkeys and red colobus made over 4 years (2660 h) at four sites, we were able to reject the null hypothesis that associations occur by chance for only one of four sites. However, a correlative approach exploring the costs and benefits of association suggests that ecological variables do influence association patterns. We found that redtail monkeys and red colobus overlapped in diet (19.2% of their foraging effort) and traveled further when in mixed-species groups than when alone. Having demonstrated this, we examined the applicability of the ecological constraints model for predicting the proportion of the time spent in mixed-species groups based on food availability. For this analysis we concentrated on red colobus from the site with 35 months of observation and demonstrated that their tendency to be in mixed- species groups was related to food availability. We used two methods to examine if mixed-species associations function to decrease predation risk. First, chimpanzees are known to prey heavily on red colobus, but rarely kill other primates. The time red colobus spent in mixed-species groups was correlated to chimpanzee density, but it was not for the other monkey species, suggesting that mixed-species groups serve to decrease predation risk. Second, when red colobus groups contain more infants and are presumably at the greatest risk of predation, they form mixed-species groups most often. These results demonstrate that the costs and benefits of mixed-species associations vary dramatically over small spatial and temporal scales. If such variation is generally the case, then studies conducted at different locations or different times could easily highlight the importance of difference selective agents in favoring mixed-species associations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002650050003
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Constraints on Group Size in Red Colobus and Red-tailed Guenons: Examining the Generality of the Ecological Constraints Model (2000)
    Springer
    International journal of primatology 21 (2000), S. 565-585 
    Details
    ISSN: 1573-8604
    Schlagwort(e): colobus ; cercopithecine ; group size ; social organization ; food abundance ; day range ; diet ; group movement ; ecological constraints model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The ecological constraints model proposes that an increase in group size will increase intragroup feeding competition and thereby constrain group size. Although this model has received wide acceptance, tests of it are based only on a few studies of species that have similar ecological requirements and social organizations, and there are reasons to question the widespread acceptance of the assumptions underpinning it. Via a 2-year study, we explored determinants of group size in species that feed on markedly different types of foods: the folivorous red colobus (Procolobus pennantii) and the frugivorous/insectivorous red-tailed guenon (Cercopithecus ascanius). We established 4 study sites approximately 15 km apart in Kibale National Park, Uganda, to examine the relationship between average group size and food availability. In both species, we quantified interdemic variation in diet, density of food trees, rate of travel, and group size. Red colobus at all sites relied heavily on leaf resources (75.5%–86.9%), but fruit (6.4%–13.9%) and flowers (2.0%–13.9%) were important in some populations. In general, red-tailed guenons fed on fruit (35.7%–59.7%), insects (14.5%–17.6%), and young leaves (12.2%–32.8%), but the amount of time allocated to these foods varied among sites. Average monthly density of trees bearing food items ranged among sites from 45 to 79 trees/ha for red colobus and from 19.6 to 67.3 trees/ha for red-tailed guenons. For both species, rate of travel was similar among sites, with one exception for red colobus. Average red colobus group size varied among sites from 14 to 40 (28 groups counted). Red-tailed guenon group size varied among sites from 11 to 24 (16 groups counted). As predicted by the ecological constraints model, group size increased with food tree density across sites for both species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005557002854
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  • 3
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    Unbekannt
    Unfavorable successional pathways and the conservation value of logged tropical forest (2004)
    Springer
    Details
    Publikationsdatum: 2004-10-01
    Print ISSN: 0960-3115
    Digitale ISSN: 1572-9710
    Thema: Biologie
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    The genetic basis of morphological differentiation in some Laminaria populations (1974)
    Springer
    Marine biology 24 (1974), S. 85-91 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Clinal differentiation of stipe traits in Laminaria (simplices) populations occurs on a gradient of exposure to wave action. Crossability tests and the production of fertile hybrids established interfertility between populations from the extremes of the morphological range. Reciprocal transplantation experiments between exposed and sheltered sites did not produce significant changes in stipe morphology. Quantitative genetic analysis of the degree of resemblance between relatives indicated a relatively high genetic component in the interpopulation differentiation. This is consistent with the results of the transplantation experiments. Within-population heritability estimates at the exposed site were low, perhaps because of intensive local stabilising selection which acts to reduce genetic variability. The question of conspecificity of L. saccharina and L. longicruris in view of these results is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00402851
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  • 5
    Digitale Medien
    Digitale Medien
    A field study of hearing in the cod,Gadus morhua L. (1973)
    Springer
    Journal of comparative physiology 85 (1973), S. 147-167 
    Details
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary 1. Field measurements of hearing in the cod,Gadus morhua L., have shown that these fish are sensitive to pure tones in the frequency range from 30 to 470 Hz with greatest sensitivity in the range 60 to 310 Hz. At the most sensitive frequencies the mean thresholds varied between -18 and -26 dB/μbar (Fig. 4). 2. Variation in the thresholds at most frequencies was related to changes in the level of ambient sea noise (Figs. 5–7). Only in calm sea conditions were unmasked thresholds obtained. The masking effect of noise was confirmed by raising the level artificially. The thresholds increased in proportion to the increase in noise level. 3. The thresholds were largely independent of the distance of the sound source over the range from 1.7 to 50m, suggesting that cod are sensitive to acoustic pressure. However, a changeover to particle displacement sensitivity was noted at frequencies below 50 Hz when the sound source was moved to within l m of the fish (Fig. 9). 4. It is concluded that the swimbladder plays an accessory role in hearing. Differences obtained in the thresholds at different sound source distances may be explained in terms of the displacement sensitivity of the otolith organs. These respond to displacements re-radiated from the swimbladder in the far-field, and to the greater incident displacement in the near-field at very low frequencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00696473
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  • 6
    Digitale Medien
    Digitale Medien
    Sensitivity to chemically diverse phagostimulants in a single gustatory neuron of a polyphagous caterpillar (2000)
    Springer
    Journal of comparative physiology 186 (2000), S. 13-19 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Key words Catalpol ; Grammia ; Gustation ; Iridoid glycoside ; Phagostimulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Caterpillars of the arctiid moth, Grammia geneura, are polyphagous, but species of Plantago are amongst their preferred food plants. A neuron in the medial styloconic sensillum on the galea has been shown to have a general phagostimulatory function. Experiments with binary mixtures and cross-adaptation have demonstrated that it responds to some sugars, to several amino acids, and also to catalpol. Catalpol is a plant secondary compound in Plantago and a phagostimulant for the caterpillars. The possible significance of combining sensitivity to nutrient compounds with sensitivity to a secondary compound is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003590050002
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  • 7
    Digitale Medien
    Digitale Medien
    Studies of the conductance changes induced in bimolecular lipid membranes by alamethicin (1972)
    Springer
    The journal of membrane biology 7 (1972), S. 325-344 
    Details
    ISSN: 1432-1424
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The addition of alamethicin to lecithin bilayers results in both voltage-dependent and voltage-independent conductance changes. In the voltage-dependent region, the slope of the conductance-voltage curve varies with the charge of the cation present in the aqueous phase. It may be shown that these effects may be accounted for by a kinetic model which incorporates the following suppositions: (1) alamethicin molecules are adsorbed at the membrane-water interface; (2) the effect of the potential is to redistribute alamethicin-cation complexes between the two surfaces of the bilayer; (3) conduction through the bilayer follows the surface interaction of approximately six alamethicin molecules; and (4) there is an assymetry in the rate constants for corresponding transitions on opposite sides of the bilayer. The effects of alamethicin are found to be approximately the same at neutral and low pH and are unchanged when bilayers are formed from phosphatidyl serine rather than lecithin. These findings are discussed in relation to current hypotheses of the molecular nature of the conduction mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01867924
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  • 8
    Digitale Medien
    Digitale Medien
    The oxygen consumption of Pennatula rubra ellis and some other anthozoans (1965)
    Springer
    Journal of comparative physiology 50 (1965), S. 363-370 
    Details
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Der Sauerstoff-Verbrauch von Pennatula rubra und anderen Pennatuliden und der See-Anemone Calliactis parasitica ist unter Anwendung der Winkler-Methode gemessen worden. Im allgemeinen hängt der Sauerstoffverbrauch dieser Coelenteraten von der O2-Konzentration im umgebenden Medium ab. Das deutet darauf hin, daß der Mechanismus der O2-Aufnahme in einer einfachen Diffusion des Sauerstoffes in die Gewebe besteht. Der O2-Verbrauch, bezogen auf das organische Trockengewicht, ist mit dem anderer wirbelloser Seetiere vergleichbar. Die Verwendung des Frischgewichtes als Bezugsgröße kann demnach irreführend sein; Pennatuliden atmen — in Anbetracht der geringen Menge organischen Materials, die sie enthalten — aktiv. Das Entoderm ist die Gewebeschicht mit dem größten Sauerstoffverbrauch. Unter Bedingungen des Sauerstoffmangels tritt bei Calliactis parasitica nur ein teilweiser Sauerstoffmangel ein, da der anschließende Sauerstoffverbrauch (unter normalen Bedingungen) nur wenig höher ist als der normale.
    Notizen: Summary The oxygen consumption of Pennatula rubra and some other pennatulids, and also of the anemone Calliactis parasitica, has been measured by a reliable method. In general, the oxygen consumption of these coelenterates is proportional to the external oxygen concentration, suggesting that the consumption mechanism relies on simple diffusion of oxygen into the cells. The oxygen consumptions per unit organic dry weight of these species are comparable with typical values for other marine invertebrates, implying that the use of wet weight as a criterion may be misleading and should be discontinued, and that pennatulids respire actively considering the small amount of organic material they contain. It is suggested that the endoderm is the major site of oxygen consumption in these animals. Calliactis parasitica, when under anaerobic conditions, incurs only a partial oxygen debt, as post-anaerobic oxygen consumption is only slightly higher than the normal rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00339424
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  • 9
    Digitale Medien
    Digitale Medien
    Non-coordinate synthesis and methylation of tRNA following excision of plant tissue (1973)
    Springer
    Planta 114 (1973), S. 227-238 
    Details
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The relationship between the synthesis and methylation of nucleic acids in tissue slices from higher plant storage organs has been investigated. Although the observed nucleic acid synthesis is mainly an expression of rRNA synthesis the highest level of methylation occurs in tRNA. Unlike the synthesis and methylation of rRNA which appears completely coupled, the methylation of tRNA is not tightly coupled to its synthesis. It is suggested that a pool of undermethylated tRNA exists in the tissue prior to incubation and that methylation of this tRNA initially controls the rate of protein synthesis in the tissue slices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00389038
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  • 10
    Digitale Medien
    Digitale Medien
    Arabinogalactan-proteins in Cichorium somatic embryogenesis: effect of β-glucosyl Yariv reagent and epitope localisation during embryo development (2000)
    Springer
    Planta 211 (2000), S. 305-314 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Key words: Arabinogalactan-protein ; Cichorium (somatic embryogenesis) ; β-d-Glucosyl Yariv reagent ; Monoclonal antibodies (JIM13 ; JIM16 ; LM2) ; Somatic embryogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract.  Direct somatic embryogenesis was induced in root tissues of the Cichorium hybrid `474' (C. intybus L. var. sativum×C. endivia L. var. latifolia). Addition of β-d-glucosyl Yariv reagent (βGlcY), a synthetic phenylglycoside that specifically binds arabinogalactan-proteins (AGPs), to the culture medium blocked somatic embryogenesis in a concentration-dependent manner with complete inhibition of induction occurring at 250 μM βGlcY. The AGP-unreactive α-d-galactosyl Yariv reagent had no biological activity in this system. Upon transfer of 250 μM βGlcY-treated roots to control conditions, somatic embryogenesis was recovered with a time course similar to that of control roots. The βGlcY penetrated roots and bound abundantly to developing somatic embryos, to the root epidermis and the stele. Immunofluorescence and immunogold labelling using monoclonal antibodies (JIM13, JIM16 and LM2) revealed that AGPs were localised in the outer cell walls peripheral cells of the globular embryo. A spatio-temporal expression of AGPs appeared to be associated with differentiation events in the somatic embryo during the transition from the globular stage to the torpedo stage. To verify βGlcY specificity, molecules that bound βGlcY were extracted from treated conditioned medium and identified as AGPs by using the same monoclonal antibodies. In addition, AGPs were found to be abundantly present in the medium during embryogenic culture. All of these results establish the implication of AGPs in embryo development, and their putative role in somatic embryogenesis is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004250000299
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