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Träfflista för sökning "hsv:(NATURVETENSKAP) hsv:(Biologiska vetenskaper) hsv:(Ekologi) srt2:(1980-1989)"

Sökning: hsv:(NATURVETENSKAP) hsv:(Biologiska vetenskaper) hsv:(Ekologi) > (1980-1989)

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1.
  • Back, C, et al. (författare)
  • High-dosage treatment of a Quebec stream with Bacillus thuringiensis serovar. israelensis : efficacy against black fly larvae (Diptera, Simuliidae) and impact on nontarget insects
  • 1985
  • Ingår i: Canadian Entomologist. - 0008-347X .- 1918-3240. ; 117:12, s. 1523-1534
  • Tidskriftsartikel (refereegranskat)abstract
    • A typical lake outlet of the Canadian Shield was treated for 15 min with a high dose (5.28 g/L s−1 of discharge) of Teknar®, a commercial formulation of Bacillus thuringiensis serovar. israelensis. Efficacy on Simuliidae larvae and impact on non-target aquatic insects of this stream were monitored using drift nets, counting plates, and artificial turf substrates along a 1000-m section downstream of the site of application. Compared with a 4-day pre-treatment average for 12-h sampling periods, drift of Simuliidae increased from 64 to 92 ×, with shorter peaks of 133–184 ×, 2–6 h after treatment. There was no evident drift increase in larvae of Ephemeroptera, Plecoptera, Trichoptera, Chironomidae, or dipterous pupae, but larvae of Blephariceridae (Diptera) were severely affected as their drift was increased by up to 50 × and remained high for 3 days. After 30 h the mortality of Simuliidae on counting plates ranged from 95 to 82% in the first 300 m, with detachment rates of 78.5–46.5%. Densities of non-target insect larvae were not reduced on the artificial substrates, except for 2 genera of Chironomidae (Eukiefferella and Polypedilum) which were reduced 26 to 39% of their original density. Drifting larvae of 1 chironomid genus (Phaenopsectra) also showed symptoms of toxemia by B.t.i. The main impact of the treatment was thus seen in 2 Nematocera families (Chironomidae and Blephariceridae) which were mainly exposed to B.t.i. sedimented on the bottom of the stream or attached to periphyton growing on rocks.
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2.
  • Petersen, Robert C., et al. (författare)
  • Influence of velocity and food availability on catchnet dimensions of Neureclipsis bimaculata (Trichoptera: Polycentropodidae)
  • 1984
  • Ingår i: Holarctic Ecology. - 0105-9327. ; 7:4, s. 380-389
  • Tidskriftsartikel (refereegranskat)abstract
    • Larvae of Neureclipsis bimaculata (Trichoptera: Polycentropodidae) construct elaborate catchnets in lotic habitats to trap small drifting invertebrate prey. Three populations located at two oligotrophic and one eutrophic site were studied in southern Sweden. Measurements were made of larval weight, net size, seston quality and quantity, and stream velocity.Neureclipsis larvae alter their net dimensions in response to both velocity and seston concentration. This was determined by comparing net structure and seston at the three locations. Larvae from the eutrophic, high quality seston site attain a significantly (P < 0.001) heavier instar V dry weight, spin a smaller catchnet, filter a volume of water dependent on body size, and slightly alter their catchnet dimensions with velocity. Larvae from the two oligothrophic sites are significantly smaller than those from the eutrophic site, spin a larger net at comparable velocities, filter a larger volume of water at comparable weights, and alter net dimensions with velocity.Estimates of silk production indicate that the net cost is minimized by spinning a very fine silken strand and by adding silk over a period of time. The cost while large is offset by a large capture rate of prey.The structure of Neureclipsis nets appears to be the result of a trade-off between maximizing food capture and minimizing hydraulic stress on the net.
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