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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Insectes sociaux 42 (1995), S. 419-426 
    ISSN: 1420-9098
    Keywords: Operational sex ratio ; male rivalry ; female choice ; inbreeding ; emigration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 105 (1996), S. 64-73 
    ISSN: 1432-1939
    Keywords: Foraging effort ; Growth ; Web-building ; Namib Desert ; Seothyra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We tested the alternative hypotheses that foraging effort will increase (energy maximizer model) or decrease (due to increased costs or risks) when food supply increased, using a Namib desert burrowing spider, Seothyra henscheli (Eresidae), which feeds mainly on ants. The web of S. henscheli has a simple geometrical configuration, comprising a horizontal mat on the sand surface, with a variable number of lobes lined with sticky silk. The sticky silk is renewed daily after being covered by wind-blown sand. In a field experiment, we supplemented the spiders' natural prey with one ant on each day that spiders had active webs and determined the response to an increase in prey. We compared the foraging activity and web geometry of prey-supplemented spiders to non-supplemented controls. We compared the same parameters in fooddeprived and supplemented spiders in captivity. The results support the “costs of foraging” hypothesis. Supplemented spiders reduced their foraging activity and web dimensions. They moulted at least once and grew rapidly, more than doubling their mass in 6 weeks. By contrast, food-deprived spiders increased foraging effort by enlarging the diameter of the capture web. We suggest that digestive constraints prevented supplemented spiders from fully utilizing the available prey. By reducing foraging activities on the surface, spiders in a prey-rich habitat can reduce the risk of predation. However, early maturation resulting from a higher growth rate provides no advantage to S. henscheli owing to the fact that the timing of mating and dispersal are fixed by climatic factors (wind and temperature). Instead, large female body size will increase fitness by increasing the investiment in young during the period of extended maternal care.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 84 (1990), S. 461-467 
    ISSN: 1432-1939
    Keywords: Web design ; Behavioral thermoregulation ; Foraging activity ; Burrowing spiders ; Eresidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the Namib Desert dunes, the web of Seothyra sp. (Eresidae) comprises sticky silk lining the edges of a horizontal mat on the sand surface. The spider sits in a silk-lined burrow attached to the mat. Arthropods become entangled in the sticky silk of the mat and are attacked and pulled into the burrow by the spider. We investigated the influence of sand surface temperature on the activity of spiders during the summer. We determined the range of thermal conditions encountered by spiders, their temperature tolerance and the influence of temperature on foraging activity and prey handling behavior. The environmental temperatures available to Seothyra vary from 17–33° C at the coolest time of day to 33–73° C at the hottest. When prevented from retreating into burrows, spiders showed signs of thermal stress at about 49° C, whereas unrestrained spiders continued to forage at web temperatures above 65° C by moving between the hot surface mat and the cooler burrow. Spiders responded quicker to prey stimuli during the hot hours of the day and completed prey capture sequences in significantly less time at surface temperatures above 49° C than below. Furthermore, captured arthropods succumbed more quickly at high surface temperatures. Our study supports the hypothesis that web design and thermoregulatory behaviors enable Seothyra to hunt under extreme thermal conditions.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 12 (1973), S. 241-247 
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Partially hardened groundnut oil and soyabean oil were heated with and without frying goods under good manufacturing practice up to 96 hours and then fed to two generations of Wistar rats in long-term feeding experiments. The over-all life span of the animals fed the unheated or heated fats respectively is practically identical and not influenced by the treatment of the fats. Furthermore our data indicate a tendency that rats fed with the unheated fats showed an increased mortality in the early periods of the experiment if compared with those groups which received the heated fats. This effect, however, is statistically significant only in case of one group out of 16 experimental groups.
    Notes: Zusammenfassung Partiell gehärtetes Erdnußöl und Sojaöl wurden mit oder ohne Bratgut, aber jeweils unter praxisüblichen Bedingungen bis zu 96 Stunden erhitzt und in einem Langzeitfütterungsversuch an 2 Generationen von Wistar-Ratten verfüttert. Die Gesamtlebensdauer der Versuchstiere ist bei Fütterung von erhitzten und nichterhitzten Fetten praktisch identisch und von der Vorbehandlung unabhängig. Die nun vollständig vorliegenden Versuchsdaten lassen aber eine Tendenz erkennen, daß Versuchstiere, die mit unbelasteten Fetten gefüttert wurden, eine erhöhte Frühsterblichkeit zeigen gegenüber solchen, die erhitzte Fette erhielten. Dieser Effekt ist aber nur bei einer von 16 Versuchsgruppen statistisch gesichert.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Fire technology 16 (1980), S. 212-226 
    ISSN: 1572-8099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract Coal pulverizing system explosions during the last few years have pointed to the need of developing inerting systems for preventing such incidents. The greater use of western subbituminous coals (with their higher tendency for spontaneous ignition) is a contributing factor to the increased frequency of coal pulverizer explosions.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 13 (1974), S. 132-142 
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The histopathological examination of 516 rats of two generations fed for whole life span deep-fried fats (partially hydrogenated peanut oil or soybean oil) showed no typical lesions according to the observations of all authors working in this field. Only the damages characteristical for normal old rats were observed. In all groups the most frequently occurring pathology were lung diseases, e.g. bronchopneumonia with extended abscess formation. Other main findings were kidney lesions in the sense of an uncharacteristic nephrosis. The incidence of liver pathology (hepatitis, necrosis, fatty infiltration) was similar in all groups and not related to the kind of treatment of the oils. Lesions of the gastro-intestinal tract were observed only rarely and there was no relation to the kind of thermal treatment of the oils. The malignant tumor rate was diminished by feeding the heated soybean oil, an observation as made by other authors.
    Notes: Zusammenfassung Die histologische Untersuchung von 516 Ratten aus 2 Generationen, die lebenslänglich mit Fritierfetten (partiell gehärtetes Erdnußöl und Sojaöl) in einer Dosis von 10% im Futter ernährt worden waren, ergab keine von der Norm abweichenden Befunde. Lediglich die für alte Ratten charakteristischen Organbefunde konnten in Übereinstimmung mit allen anderen über dieses Gebiet arbeitenden Autoren festgestellt werden. In allen Gruppen war der häufigste Befund Bronchopneumonien mit ausgedehnten Abszeßbildungen. Ein anderer häufig zu erhebender Befund waren Nierenveränderungen im Sinne einer uncharakteristischen Nephrose. Pathologische Leberbefunde (Hepatitis, Nekrosen, starke Verfettung) wurden in allen Gruppen praktisch gleichmäßig verteilt gefunden und waren unabhängig von der thermischen Behandlung der Fette. Schädigungen des Magen-Darm-Traktes traten nur sehr selten auf und zeigten keine Korrelation zu der Art der Behandlung der Fette. Die Rate an malignen Tumoren war — in Übereinstimmung mit Angaben anderer Autoren — bei den Gruppen, die thermisch behandelte Sojaöle erhalten hatten, kleiner als in der Kontrollgruppe, der das unerhitzte Sojaöl verfüttert worden war.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 15 (1976), S. 251-254 
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Long-term feeding of frying oil to male rats increases significantly the activity of the drug and toxic substances metabolizing microsomal enzym system. This effect was also seen in the females, but only statistically insignificant.
    Notes: Zusammenfassung Die langfristige Verfütterung von Fritierfett an männliche Ratten bewirkt eine statistisch signifikante Steigerung der Aktivität des mikrosomalen Drogen und toxische Substanzen entgiftenden Enzymsystems. Diese Wirkung war auch bei den Weibchen vorhanden, jedoch statistisch nicht signifikant.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 15 (1976), S. 247-250 
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The hematological and chemical examination of the 3rd generation of rats fed soy bean oil used for fish frying showed not any abnormal data.
    Notes: Zusammenfassung Die hämatologischen und klinisch-chemischen Untersuchungen der dritten Generationen von Ratten, die mit zum Fritieren verwendetem Sojaöl ernährt worden waren, ergaben keine von der Norm abweichenden Befunde.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 14 (1975), S. 175-183 
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Die Verfütterung von Fritierfetten an Ratten ergab in allen untersuchten Parametern keine Unterschiede gegenüber den Verhältnissen bei den Kontrolltieren, welche die entsprechenden nichterhitzten Fette (partiell hydriertes Erdnußöl, Sojaöl) in derselben Menge und über den gleichen Zeitraum erhalten hatten. Untersucht wurden: Konzentration der Plasmalipide einschließlich des Gesamtcholesteringehaltes, Elektrophorese der Plasmalipoproteine, Fettsäurezusammensetzung der Plasmalipide und des Depotfetts sowie Menge und Zusammensetzung des Unverseifbaren einschließlich des Gehaltes an den polycyclischen Kohlenwasserstoffen. In In-vitro-Versuchen untersuchten wir die Wirkung der Pankreaslipase auf nichterhitzte und erhitzte Fette.
    Notes: Summary In feeding experiments no differences could be observed when used frying fats were fed to rats in the same amount and over the same period if compared with the unheated fats (partially hardened groundnut oil, soyabean oil). In details we investigated: concentration of plasma lipids including content of total cholesterol, electrophoresis of plasma lipoproteins, fatty acid composition of plasma lipids and of adipose tissue. Amount and composition of the unsaponifiable matter in heated and unheated fats as well as the content of polycyclic aromatic hydrocarbons were determined. In in-vitro experiments we investigated the effect of pancreas lipase on these fats.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 9 (1969), S. 363-387 
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Soya bean oil and partially hardened groundnut oil, which can be regarded as completely different with respect to fatty acid composition and properties, were heated in a normal commercial fryer both with and without food and then subjected to chemical and physiological tests. In the chemical part of the work the attempt was made to make reasonably reliable statements as to the condition of the cooking fat using the equipment and methods available to a works laboratory in the food industry or a laboratory of the official food inspection authorities. The physiological part consisted of feeding the cooking fats to white rats; the report pays particular attention to protein efficiency. The results of the long-term tests over several generations, especially the histological findings, will be dealt within a later communication. No correlation was established between the chemical analysis data and the results of the feeding trials. Even cooking fats which had been used for a much longer period than is normal practice in the industry showed no adverse effect on the growth and protein efficiency of the laboratory rats, although in some cases the fats' chemical analysis data already deviated markedly from those of the original product. In view of the results obtained so far in the animal tests and in conformity with guidelines issued by the Hamburg health authorities it is recommended that the fat be changed completely once a week when frying fish products, using a maximum temperature of 180 °C.
    Notes: Zusammenfassung Sojaöl und partiell gehärtetes Erdnußöl, die von Zusammensetzung und Eigenschaften her als extrem verschieden anzusehen sind, wurden in einer handelsüblichen Friteuse, teils mit Bratgut, teils ohne solches erhitzt und dann sowohl chemisch als auch physiologisch untersucht. Im chemischen Teil der Arbeit wird der Versuch unternommen, mit den Mitteln, die einem Kontrollaboratorium der Lebensmittelindustrie oder einem Laboratorium der amtlichen Lebensmittelüberwachung zur Verfügung stehen, und den dort anwendbaren Methoden einigermaßen sichere Aussagen über den Zustand eines Bratfettes zu machen. Der physiologische Teil befaßt sich mit Verfütterung der Bratfette an weiße Ratten, wobei speziell über die Protein-Efficiency berichtet wird. Die Ergebnisse der über mehrere Generationen laufenden Langzeitversuche, insbesondere die histologischen Befunde, werden Gegenstand einer späteren Mitteilung sein. Eine Korrelation zwischen den Daten der chemischen Analysen und den Resultaten der Tierversuche konnte nicht festgestellt werden. So zeigten selbst Bratfette, die weit über das in der industriellen Praxis übliche Maß hinaus verwendet worden waren, keinen abträglichen Einfluß auf Wachstum und Protein-Efficiency der Versuchstiere, obwohl die chemischen Kennzahlen der Fette zum Teil bereits erheblich von denjenigen der Ausgangsprodukte abwichen. Unter Berücksichtigung der bisherigen Ergebnisse der Fütterungsversuche und in Übereinstimmung mit einem Merkblatt der Hamburger Gesundheitsbehörde wird empfohlen, beim Braten von Fischen und Fischprodukten in Friteusen bei einer Maximaltemperatur von 180 °C das Bratfett einmal pro Woche vollständig zu erneuern.
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