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  • Operational sex ratio  (1)
  • PCBs  (1)
  • Spiders  (1)
  • 1995-1999  (3)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Insectes sociaux 42 (1995), S. 237-248 
    ISSN: 1420-9098
    Schlagwort(e): Spiders ; Stegodyphus ; competition ; tolerance ; sociality ; preadaptation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In spiders, known as potentially cannibalistic, mutual tolerance is one important requirement for group life. Using the subsocial spiderStegodyphus lineatus which possibly resembles the ancestors of the social species, the effects of competition were investigated in the laboratory. When dispersal was prevented, spiderlings were capable of living in groups. The intensity of competition for food among spiders in groups was varied experimentally by varying group size or the relative size differences of individuals. Body mass and mortality were compared in the different experiments. Prey availability, the size of the spiders and initial body size differences among group members all influenced the survival probability and growth of the spiders. Spiders of equal size tolerated each other with a higher probability than spiders of different sizes. Feeding in groups was always disadvantagous even for the largest spiders.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Insectes sociaux 42 (1995), S. 419-426 
    ISSN: 1420-9098
    Schlagwort(e): Operational sex ratio ; male rivalry ; female choice ; inbreeding ; emigration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Sexual competition is shown to occur in the social spiderStegodyphus dumicola (Eresidae). While the secondary sex ratio inS. dumicola was female-biased, the overall operational sex ratio (numbers of breeding males to breeding females over the season) showed no strong female bias. Males matured before females and had a shorter lifespan than the females. Mating took place in the natal colony. Males fought over access to the few mature females available early in the reproductive season, but females appeared to control the duration of mating. Later in the season, some adults of both sexes dispersed alone to breed elsewhere. We conclude that different rates of maturation between the sexes within a colony provide the opportunity for females that mature early in the season to be choosy in selecting a mate and this forces males to compete. Early reproduction may be beneficial for both females and males, because the offspring of females that reproduce early may have a competitive advantage over later (and smaller) offspring in the colony.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 104 (1998), S. 113-124 
    ISSN: 1573-2932
    Schlagwort(e): Aroclor 1248 ; PCBs ; soil profiles ; volatilization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract PCB mixtures in surface deposits composed of core sand and ash from an aluminum foundry are enriched (3.6–9.4%) in chlorine percentage relative to deeper horizons. The deeper materials closely match (R2 = 0.902–0.962) Aroclor 1248, the aroclor used on-site and recovered from the floor inside the foundry (R2 = 0.998). This similarity suggests the more deeply buried PCBs have been stable and immobile for a 20–40 yr period. Chlorine enrichment upward is interpreted as the result of volatilization of lower and orthochlorinated congeners from surficial materials during repeated water evaporation. These results suggest surficial deposits contaminated by PCBs may be a significant source of lower ortho-chlorinated PCB congeners to the atmosphere and that buried PCBs can remain unchanged for decades. Comparison with sediments contaminated with Aroclor 1248 and known to have undergone anaerobic microbial dechlorination, indicates that Aroclor 1248 can be transformed to PCB mixtures enriched or depleted in chlorine by environmental processes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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