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  • 1
    ISSN: 1570-7458
    Keywords: repellent ; Ixodes ricinus ; host-seeking ; bioassay ; tick ; DEET
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A bioassay was developed to examine the response of ticks towards potential repellents that may protect vertebrates against tick bites. Such tick repellents must be effective despite the unavoidable presence of various attractive host-derived stimuli. Therefore, a moving-object-bioassay (MO-bioassay) was developed that mimicks body warmth and movement of vertebrates by a rotating and heated drum. Compounds which were tested for their effects on ticks were applied onto a small elevated area of the drum. Ticks were allowed to approach the drum by walking on a glass rod which ended ≈1 mm away from the local elevation. Ticks could cling to this elevation that intermittently passed by, whereas the remaining drum surface was too far away from the tip of the rod to be contacted by the ticks. Without the presence of any repellents, 85.5% of 600 hungry, field-collected Ixodes ricinus nymphs moved to the heated, rotating drum within 2 min. Further experiments with unfed I. ricinus nymphs were performed to test whether one established and two potential tick repellents elicit an avoidance reaction in the ticks despite the proven attractiveness of the drum. Freshly applied DEET (N,N-diethyl-m-toluamide) at a concentration of 0.11 mg cm−2 proved active as a repellent in the MO-bioassay over a distance of a few mm as well as by direct contact. A similar repellent effect was observed with (−)-myrtenal at 1 mg cm−2, but not at 0.1 mg cm−2, indicating that this terpenaldehyde is a weaker repellent for I. ricinus nymphs than DEET. No repellent effect was observed with camphor (0.1 mg cm−2). The MO-bioassay thus is a rapid, simple and low-cost test method allowing the investigation of tick host-contact behaviour as well as the screening of candidate repellents which are either perceived as volatiles or via contact chemoreception.
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  • 2
    ISSN: 1573-1561
    Keywords: Galeruca tanaceti ; Coleoptera ; Chrysomelidae ; anthraquinones ; eggs ; larvae ; hemolymph ; ovaries ; Tanacetum vulgäre ; Achillea millefolium ; feeding deterrence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The overwintering eggs and the larvae of the leaf beetleGaleruca tanaceti (L.) contain hydroxylated anthraquinones. In both developmental stages, l,8-dihydroxy-3-methylanthraquinone (= chrysophanol) and 1,8-di-hydroxyanthraquinone (= chrysazin) were detected by GC-MS and GC-FTIR analyses. In the eggs, chrysazin was found only in traces. Anthraquinones were also present in ovaries and hemolymph of gravid females, which were investigated in order to examine the incorporation of these substances into the eggs. Neither in acidified nor in nonacidified extracts of the host plantsTanacetum vulgäre L. andAchillea millefolium L. were anthraquinones found. The activity of these anthraquinones as chemical defense substances was proved in bioassays with the antMyrmica ruginodis NYL. Further possible biological significances of anthraquinones are discussed.
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  • 3
    ISSN: 1573-1561
    Keywords: Coleoptera ; Chrysomelidae ; Chrysomela lapponica ; larval secretion ; defense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The defensive secretion ofChrysomela lapponica larvae, which is produced by nine pairs of exocrine dorsal glands, has been chemically analyzed. TheC. lapponica larvae were kept in the laboratory on leaves of either birch (Betula pendula), alder (Alnus glutinosa), or willow (Salix fragilis). Larvae developed normally on birch and willow, whereas those on alder died within a few days. GC-MS analyses of the secretion of larvae on birch and willow revealed that the composition of this secretion differs distinctly from the known ones of several otherChrysomela species feeding exclusively on Salicaceae. In the exocrine secretion of larvae on birch, 69 compounds were identified, which included the main components isobutyric acid, 2-methylbutyric acid, and esters of the two. Several of the esters have not been reported previously from nature. The alcoholic components of the esters may be hydrolysis products ofBetula glycosides. Most components of the secretion of larvae feeding on birch were also found in the secretion of larvae feeding on willow. In addition, major amounts of benzoic acid and salicylalcohol were present in the secretion of the larvae feeding on willow.C. lapponica obviously acquires salicylalcohol by hydrolysis of salicin from willow leaves. However, in contrast to otherChrysomela species,C. lapponica larvae oxidize only traces of salicylalcohol to salicylaldehyde. The repellent activity of single authentic compounds of the secretion of larvae feeding on birch and willow, respectively, was tested in laboratory bioassays with ants (Myrmica sabuleti). Biosynthetic pathways to some identified compounds are suggested and discussed under evolutionary and functional aspects.
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  • 4
    ISSN: 1570-7458
    Keywords: Lepidoptera ; Spodoptera littoralis ; oviposition ; deterrents ; feeding ; larval experience ; induction ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Females ofSpodoptera littoralis Boisd. (Lepidoptera: Noctuidae) with different feeding experiences during their larval development were tested for their ovipositional response to methanol extracts of larval frass and semisynthetic diets. The effect of the following frass, diet and diet component extracts was tested: (a) frass fromS. littoralis orAgrotis segetum larvae fed on a potato-based diet; (b) frass fromS. littoralis larvae fed on a wheat germ-based diet; (c) potato and wheat germ-based diets; and (d) potatoes and wheat germ. Ovipositing females without prior experience of the potato diet were deterred by extracts of: (1) larval frass from either species fed on potato diet; (2) the potato-based diet; (3) potato. Also females with experience of the potato diet during only a part of their larval development were deterred from oviposition by frass of larvae reared on the potato diet and by the diet itself. However, for females reared on the potato diet for their entire larval development, oviposition was no longer deterred by either of the three extracts listed above. Extracts of: (1) frass from larvae of either species reared on wheat germ diet: (2) the wheat germ diet; or (3) wheat germ did not significantly affect oviposition. Females with ablated antennae were still deterred by frass extracts from larvae fed on potato diet, when they had been reared on the wheat germ diet. In feeding experiments, larvae of larval stage one and of larval stage three-four reared on either of the two diets preferred to feed on the wheat germ diet. However, the preference was significantly stronger for larvae with no prior contact with the potato diet. The effect of larval experience on the loss of oviposition-deterring activity by extracts of larval frass, diets and diet components is discussed in view of induction and selection.
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  • 5
    ISSN: 0022-1910
    Keywords: Benzaldehyde ; Chemoreceptors ; Cotton ; Oviposition deterrent ; Sensillum ; Synergism ; Terpenes
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 6
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and ...
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  • 7
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 72 (1985), S. 485-486 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 9
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract  The role of a general green leaf volatile (glv) in host finding by larvae of the oligophagous chrysomelid Cassida denticollis was investigated using a new bioassay which takes into account the need for neonate larvae of this species to climb fresh host plants from the ground. A "stem arena" was designed in which plant stems of the host, tansy (Tanacetum vulgare), and stem dummies (tooth picks), both wrapped in perforated filter paper, were offered to neonate larvae. The wrapping allowed olfactory responses to be tested by preventing access to contact stimuli of stems and dummies. Larvae significantly preferred to climb the wrapped tansy stems over dummies after a period of 15 min. The test glv, (Z)-3-hexen-1-ol, was not attractive when applied to dummies. However, when the glv was applied to the bottom of the arena, the ability of larvae to discriminate between host stems and untreated dummies was significantly enhanced. More larvae climbed wrapped host stems than dummies even within 5 min. While numerous other herbivorous insects are known to be directly attracted by glv, this study shows that a singly offered glv on its own is unattractive to an herbivore but enhances the herbivore's ability to differentiate between host and nonhost plants.
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  • 10
    ISSN: 1420-9071
    Keywords: Chrysolina fuliginosa ; Coleoptera ; Chrysomelidae ; beetles ; cardenolides ; eggs ; glands ; chemical defence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Besides the known sarmentogenin 3-O-β-D-allopyranoside (1) and digitoxigenin-3-O-[β-D-xylopyranosyl-(1→4)-2′, 3′-di-O-acetyl-β-D-allopyranoside] (4), four new cardiac glycosides (2, 3, 5 and6) have been isolated from the defensive glands of adults ofChrysolina fuliginosa. The structures of the new compounds were determined by1H NMR at 600 MHz and FABMS. Compounds1–6, present in the adults ofC. fuliginosa, have also been identified in the eggs.
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