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  • phototaxis  (3)
  • Key words Ground beetles  (1)
  • 1
    ISSN: 1432-1939
    Keywords: Key words Ground beetles ; Biodiversity ; Genetic differentiation ; Habitat fragmentation ; Wing polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Enzyme and dispersal polymorphisms of the saltmarsh carabid beetles Pogonus chalceus and Dicheirotrichus gustavii were studied in European populations varying in size and in isolation in space and time. D. gustavii, a constantly fullwinged species, has a larger genetic diversity and a smaller genetic differentiation between populations than the wing-polymorphic P. chalceus. Clear relationships between population or site characteristics and genetic structure were not observed, except for the special position taken by some small populations in both species. The dispersal power of P. chalceus in small populations is larger than in large populations, suggesting that these populations are unstable and/or young. Small populations, however, do not always show a lower genetic diversity than large populations, as would be expected from genetic drift. Dispersal power in P. chalceus declines with increasing age of the saltmarsh, probably due to continuous emigration of winged individuals. Age and size of saltmarshes, although difficult to study independently, both appear to be important in determining the genetic structure of saltmarsh beetles. Maximum diversity in both parameters is therefore recommended as an optimal nature conservation strategy.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: phototaxis ; vertical migration ; temporary pools ; Anostraca ; Streptocephalus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phototactic behaviour of adults of the Sudanese fairy shrimpStreptocephalus probiscideus was studied under laboratory conditions. Males were less negatively phototactic than females. This was also evident when colour filters were used. females only became little less negatively phototactic under yellow light, whereas males showed a strong positively phototactic response. The response to the positioning of a yellow filter was stronger than to the use of a red or blue filter for both sexes. The laboratory findings were compared with casual field observations onStreptocaphalus torvicornis that indicate differential vertical distribution between the sexes and a nocturnal vertical migration. Migratory behaviour with ascent starting at dusk is also predicted forS. proboscideus. This behaviour may reduce common stress factors in desert pools such as photodamage, visual predation pressure, and high surface temperatures.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5117
    Keywords: phototaxis ; genotype ; vertical migration ; Daphnia magna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using a cloning technique, we revealed the existence of three phototactically distinct types in Daphnia magna, viz. negatives, positives, and “gipsies”. The latter migrate continuously between a low and a high light intensity. The expression of this behaviour is genetically determined, although positives and negatives can reversibly switch into “gipsies”. It is proposed that two opposite genotypes exist, with the “gipsy” behaviour epigenetically induced. All juveniles behave more or less uniformly, irrespective of their origin. The phototactic responses develop rather late during ontogenesis.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 225 (1991), S. 217-227 
    ISSN: 1573-5117
    Keywords: Cladocera ; Daphnia magna ; crosses ; genetics ; phototaxis ; vertical migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Daphnia magna clones, isolated from different natural populations, were inbred and crossbred. Some aspects of the heredity of the phototactic behaviour, quantified by an index, were analysed. Heritability in the broad sense was determined for several assemblages of clones through calculation of the clonal repeatability. Heritability sensu strictu was determined by offspring-parent regressions. Frequency distributions of a phototactic index of several inbred and crossbred families are given. The results indicate a significant contribution of additive genetic variance to the total phenotypic variance. Comparison of heritability estimates suggests an important genetic interaction component. Some implications of these results on the variability of vertical migration patterns in natural populations are discussed.
    Type of Medium: Electronic Resource
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