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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 73 (1987), S. 389-392 
    ISSN: 1432-1939
    Schlagwort(e): Mate competition ; Parasitism ; Malaria ; Lizards ; Sceloporus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The effect of malarial parasitism on the ability of male western fence lizards, Sceloporus occidentalis, to compete for access to females was assessed experimentally. Pairs of male lizards, one infected with the malarial parasite, Plasmodium mexicanum, and the other not infected, were matched by size and color and placed in large seminatural outdoor enclosures along with an adult female lizard. Infected males displayed to females and to other males less often than did noninfected male lizards. Noninfected lizards were dominant in social interactions more often than malarious animals, based on duration and intensity of agonistic encounters toward the other male, and time spent with the female. Thus, malarial infection hinders the ability of male fence lizards to compete for mates.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 97 (1994), S. 326-332 
    ISSN: 1432-1939
    Schlagwort(e): Parasite ; Malaria ; Lizards ; Africa Plasmodium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Plasmodium giganteum and P. agamae, parasites of the rainbow lizard, Agama agama, in West Africa were studied to determine the nature of any interspecific interactions between the two malaria species. The plasmodia are distributed in A. agama throughout the mesic zone of Africa; P. agamae is sometimes found as a solitary malaria species in populations of the lizard, but P. gigateum has not been found alone. In 3170 lizards from Sierra Leone the prevalence of lizard malaria at 22 sites varied considerably (8–90% of lizards were infected), but the ratio of the two species was similar among sites (52–91% P. agamae). Larger lizards were more often infected. Mixed infections occurred 2–5 times more often than expected by chance. Parasite density within individual hosts, or parasitemia, was similar for each species when alone or in mixed infection. Natural infections followed in laboratory lizards stayed at constant levels for as long as 211 days. The two species use different classes of host cells (P. giganteum in immature cells and P. agamae in mature erythrocytes) and may have different periods of peak transmission. Analysis of the data does not support a neutral relationship between P. giganteum and P. agamae, nor ongoing competition for resources or heterologous immunity. The data best support facilitation in which P. agamae alters the host in a way that allows more successful establishment of P. giganteum.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 92 (1992), S. 58-64 
    ISSN: 1432-1939
    Schlagwort(e): Parasite ; Competition ; Malaria ; Anolis ; Lizards ; Caribbean
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary On many small Caribbean islands, two species of Anolis lizard coexist, but the two are typically very different in body size. The two Anolis of St. Maarten, however, are exceptional because they are similar in size and are known to be strongly competitive. One species, A. gingivinus, appears the stronger competitor and occurs throughout the island; the other, A. wattsi, is found only in the central hills. The malarial parasite Plasmodium azurophilum very rarely infects A. wattsi, but in some locations is very common in A. gingivinus. Wherever malaria infects A. gingivinus, A. wattsi is present, but wherever malaria is absent, only A. gingivinus occurs. This pattern of coincidence of malaria and coexistence of both Anolis is observed over distances of only a few hundred meters. The parasite infects both red and white blood cells of A. gingivinus and causes important pathology: immature erthrocytes increase in abundance, blood hemoglobin decreases, monocytes and neutrophils increase, and infected white cells are less likely to produce acid phosphatase. These results argue that malaria mediates competition between the two species and determines the present distribution of the lizards on St. Maarten. This kind of parasite-mediated competition could be common if susceptibility to parasitic infection varies among competitors. The distribution of malaria in the Anolis of Caribbean islands suggests this parasite can play an important role in Anolis community ecology.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 78 (1989), S. 158-164 
    ISSN: 1432-1939
    Schlagwort(e): Parasites ; Malaria ; Lizards ; Sexual selection ; Sexual dimorphism ; Hamilton/Zuk hypothesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Hamilton and Zuk (1982) proposed that the quality of male showy traits reflects genetically-based resistance to parasites and can be used by females to select mates that are less prone to parasitic attack. The hypothesis requires that a particular state of a variable showy trait should be associated with parasite infection. We tested this idea with a population of western fence lizards, Sceloporus occidentalis, infected with the malarial parasite, Plasmodium mexicanum. Ventral color pattern is strongly dimorphic in fence lizards and varies greatly among males in this population. Malaria-infected males exhibited significantly more black and less pale on their ventral surface than did noninfected males of similar body size. This difference was not a function of differing ages of infected and noninfected animals of the same body size. However, logistic regression demonstrated that females using male ventral color as a gauge of infection status would only marginally improve their chance of choosing a noninfected lizard over random selection of mates.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1434-6079
    Schlagwort(e): 34.50.H ; 34.70 ; 79.20.N
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The linear and circular polarization of the Li(2p−2s) emission has been measured for Li+ collisions with cesiated and oxydized cesiated W(110) surfaces, Cs-W(110) and O/Cs-W(110), at impact energies below 1 keV for an incidence angle of 5 degrees with respect to the surface plane. The cesium coverage has been varied between zero and the saturation coverage at room temperature. Although the excitation of the projectile seems to occur in a binary collision with only one Cs adatom, the presence of the surface influences the total photon yield by Auger deexcitation, and the circular polarization by affecting the energetic separation of the Li(2p) substates close to the surface.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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