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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 213 (2002), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The detection of ancient microbial DNA offers a new approach for the study of infectious diseases, their occurrence, frequency and host–pathogen interaction in historic times and populations. Moreover, data obtained from skeletal and mummified tissue may represent an important completion of contemporary phylogenetic analyses of pathogens. In the last few years, a variety of bacterial, protozoal and viral infections have been detected in ancient tissue samples by amplification and characterization of specific DNA fragments. This holds particularly true for the identification of the Mycobacterium tuberculosis complex, which seems to be more robust than other microbes due to its waxy, hydrophobic and lipid-rich cell wall. These observations provided useful information about the occurrence, but also the frequency of tuberculosis in former populations. Moreover, these studies suggest new evolutionary models and indicate the route of transmission between human and animals. Until now, other pathogens, such as Mycobacterium leprae, Yersinia pestis, Plasmodium falciparum and others, have occasionally been identified – mostly in single case studies or small sample sizes – as well, although much less information is available on these pathogens in ancient settings. The main reason therefore seems to be the degradation and modification of ancient DNA by progressive oxidative damage. Furthermore, the constant risk of contamination by recent DNA forces to take time and cost effective measures and renders the analysis of ancient microbes difficult. Nevertheless, the study of microbial ancient DNA significantly contributes to the understanding of transmission and spread of infectious diseases, and potentially to the evolution and phylogenetic pathways of pathogens.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 22 (1989), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Resting eggs (ephippia) of Daphnia galeata, D. hyalina, D. cucullata and D. galeata X D. hyalina hybrids were collected from the upper 8 cm of sediments at various water depths from two glacial lakes in the Northern Federal Republic of Germany.2. The horizontal distribution of ‘intact’ ephippia (i.e. those containing two apparently healthy eggs) was extremely patchy, with mean densities in the upper 8 cm ranging from 1325 to 113,907 m−2 (coefficient of variation, C=65.5%; Schöhsee, Holstein) and 25,343–159,143 m−2 (C=58.5%; Kel-lersee. Holstein). Ephippial densities were greatest in sediments from deep waters. The highest densities of intact ephippia were in the upper 4 cm of sediment, with progressively fewer with increasing depth.3. A proportion of eggs obtained from sediments during autumn (September-November 1985) and spring (March-May 1986) were exposed to continuous light (approximately 18 W m−2) at three temperatures (6, 12, 20°C), and the incidence of hatches recorded.4. Hatching success was consistently low (maximum 14.4%), with most hatching occurring at 12°C. There was no significant difference between the hatching success of ephippia collected during autumn and spring. Decapsulation of ephippial eggs inhibited hatching. Hatching was highly synchronous within each treatment, and the pattern did not differ significantly with sediment depth, though hatching success was lower in deep sediments. A huge reservoir of ephippia is present in lake sediments, of which a proportion may remain viable for many years. Periodic recruitment of hatchlings to the pelagic population may provide an important mechanism for the maintenance of genetic diversity in Daphnia populations, as well as affecting rates of evolutionary change.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 22 (1989), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. To investigate the contribution of hatchlings from lake-Daphnia resting eggs (ephippia) to population and community structure, hatching was monitored in situ from April to November 1986 in two north German lakes. Hatching traps were placed on the sediments and the incidence, genetic and species composition of ephippial hatchlings determined twice-weekly.2. Hatching began in April after the thawing of ice. and continued for 3–4 weeks until the lakes stratified. There was no obvious relationship between the onset and duration of hatching and the environmental variables recorded, namely Secchi depth, surface temperature, temperature and oxygen concentration at the sediment-water interface.3. Among the hatchlings were D. galeata, D. hyalina and their interspecific hybrid.4. In the lake which contained overwintering animals the number of ephippial hatchlings was approximately one third of the total number of juveniles present in the lake.5. In the second lake, no adults were recorded during winter and the population was probably founded by ephippial hatchlings alone. There was good agreement, in the short term, between the proportion of each species represented among hatchlings and the subsequent species composition in the lake.6. The hatchlings were genetically diverse, and alleles were representative of those alleles present in contemporary populations.
    Type of Medium: Electronic Resource
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