| 1. |
|
|
| 2. |
- Olivares, Manuel, et al.
(författare)
-
Non-lethal effects of the predator Meganyctiphanes norvegica and influence of seasonal photoperiod and food availability on the diel feeding behaviour of the copepod Centropages typicus
- 2020
-
Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 42:6, s. 742-51
-
Tidskriftsartikel (refereegranskat)abstract
- Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed the influence of seasonal photoperiod and prey availability on the intensity of copepod feeding rhythms. We did not detect any large effect of krill presence on the diel feeding behaviour of copepods, either in day-night differences or total daily ingestions. Seasonal photoperiod and prey availability, however, significantly affected the magnitude of copepod feeding cycles, with larger diel differences in shorter days and at lower prey concentrations. Therefore, the role of non-lethal direct effects of predators on the diel feeding activity of marine copepods remain debatable and might not be as relevant as in freshwater zooplankton.
|
|
| 3. |
- Tiselius, Peter, 1958, et al.
(författare)
-
Sensory capabilities and food capture of two small copepods, Paracalanus parvus and Pseudocalanus sp.
- 2013
-
Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590. ; 58:5, s. 1657-1666
-
Tidskriftsartikel (refereegranskat)abstract
- Detection, handling, and selection of prey are key features of suspension-feeding copepods. Using high-speed video, we determined detection distances and durations of all elements of the food gathering process in two small calanoid copepods, Paracalanus parvus and Pseudocalanus sp. Animals were freely swimming and presented with various phytoplankton species with equivalent spherical diameters ranging from 7 µm to 33 µm. Prey detection occurred very close—within a few cell radii—to the second antennae (53% of the cases) or the maxilliped (42%). There was no effect of prey size on detection distance, but larger prey caused a significantly longer handling time. Post-detection processing of the cells was exceedingly fast. The time from detection to the cell being placed at the mouth lasted 35 ± 19 ms and rejection of unwanted cells 61 ± 21 ms. Grooming of antennules and carapace occurred intermittently and lasted 215–227 ms. The weak feeding current and fast response of the copepods allowed ample time for detection of cells entrained in the feeding current and no distant olfaction was observed. Modeled effect of cell size on cell surface concentration of cue chemicals show that only cells with a radius larger than ∼ 15 µm may be detected chemically and that only very much larger and/or very leaky cells can be detected at distance. Copepods have elaborate and exceedingly fast handling techniques that allow effective prey detection and capture, but there is no evidence of remote chemically mediated sensing when feeding on algal cells up to a size of 35 µm.
|
|
