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Träfflista för sökning "WFRF:(Jonsson Per R. 1957) srt2:(1995-1999)"

Search: WFRF:(Jonsson Per R. 1957) > (1995-1999)

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  • Loo, Lars-Ove, 1954, et al. (author)
  • Passive suspension feeding in Amphiura filiformis (Echinodermata: Ophiuroidea): Feeding behaviour in flume flow and potential feeding rate of field populations
  • 1996
  • In: Mar Ecol-Progr Ser. - 0171-8630. ; 139:1-3, s. 143-155
  • Journal article (peer-reviewed)abstract
    • Experimental studies in a laboratory flume show that the sediment-living brittle-star Amphiura filiformis captures suspended particles. Feeding activity is a function of now velocity with few animals extending feeding arms in still water. Flow velocity also affects the orientation of feeding arms, and we suggest that this orientation is partly controlled by A. filiformis. By combining field measurements of current velocity and seston concentration with morphometrics and filtration models, a theoretical encounter rate of suspended particles was calculated for A. filiformis. In terms of organic content, A. filiformis can potentially balance growth and respiration with ingested seston although balance will strongly depend on retention efficiency and particle quality. Detailed measurements of flow around feeding arms revealed complex now patterns that will limit the applicability of available models of food encounter for passive suspension feeders, but our sensitivity analysis indicates that suspended aggregates may be especially important in the nutrition of this species.
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3.
  • Tiselius, Peter, 1958, et al. (author)
  • Effects of copepod foraging behavior on predation risk: An experimental study of the predatory copepod Pareuchaeta norvegica feeding on Acartia clausi and A-tonsa (Copepoda)
  • 1997
  • In: Limnology and Oceanography. - 0024-3590. ; 42:1, s. 164-170
  • Journal article (peer-reviewed)abstract
    • The effect of foraging behavior on predation risk was studied by exposing the two small calanoid copepods Acartia clausi and Acartia tonsa to 0 or 1 ppm (similar to 1,500 cells ml(-1)) of the diatom Thalassiosira weissflogii and to presence of the predator Pareuchaeta norvegica. In filtered water, predation rate was the same on the two species. In algal suspension, predation rate on A. clausi was half that in Filtered water and half that on A. tonsa. Video observations revealed distinct differences in motility of Acartia depending on algal concentration. Both species performed frequent short feeding bouts in algal suspension; nonfeeding copepods in filtered water alternately sank or adjusted their vertical distribution by stronger jumps. Jump frequency nearly doubled for A. clausi in filtered water. but no significant difference was observed for A. tonsa. To explain the predation, assuming that P. norvegica is a rheotactic predator, we developed a model of potential hydrodynamic disturbance associated with each foraging behavior. Increased encounter rate with P. norvegica caused by frequent strong jumps by A. clausi in the absence of algae could explain >40% of the observed increase in predation rate. For A. tonsa, jump frequencies and predation rates were similar in both food treatments, which is in accordance with the model.
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