| 1. |
|
|
| 2. |
- Johansson, Jonas, et al.
(författare)
-
Active selection for large guppies, Poecilia reticulata, by the pike cichlid, Crenicichla saxatilis
- 2004
-
Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 105:3, s. 595-605
-
Tidskriftsartikel (refereegranskat)abstract
- Size-selective predation has been proposed to be one important evolutionary force shaping life-history traits in guppies (Poecilia reticulata). Populations living in the presence of the ring-tailed pike cichlid (Crenicichlasaxatilis) are smaller, mature earlier, allocate more energy to offspring and get more and smaller young than guppies in localities without Crenicichla. We investigated if Crenicichlasaxatilis is a size-selective predator, if the selectivity is a result of active choice and if the optimal prey size can be explained according to an optimal foraging model. In single-prey experiments we quantified the predators' pre-capture costs (time), capture success, and post-capture costs (time) for four different prey sizes spanning from 10 to 40 mm total length. To see which of the components of the prey cycle the predator takes into account for its choice, we then predicted prey values and optimal prey size with 6 different models that included one or more of the prey cycle components. In two multiple prey experiments, the cichlids were given the choice of the two and four different prey sizes simultaneously. Crenicichlasaxatilis actively selected the largest guppies in both cases. The three prey-value functions that included handling time (post-capture cost) did not accurately predict the prey choice. Instead the prey-value functions that took into account pre-capture cost (approach and attack time) were able to correctly predict the choice of the largest guppy size, suggesting that pre-capture costs may be more important than post-capture costs for prey choice in Crenicichlasaxatilis. The study confirms that Crenicichlasaxatilis is a size-selective predator selecting large guppies, while earlier evidence for selectivity for large prey in Crenicichla cichlids has been weak and equivocal. Our result strengthen the possibility that size-selective predation is a mechanism in life-history evolution in guppies.
|
|
| 3. |
- Mattsson, Sören, et al.
(författare)
-
Swedish Cancer Society radiation therapy research investigation
- 2002
-
Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 41:7-8, s. 596-603
-
Tidskriftsartikel (refereegranskat)abstract
- In an investigation by the Swedish Cancer Society, the present status, critical issues and future aspects and prospects were described by an expert group for each of nine major areas of radiation research. A summary of the investigation is presented in this report. A more extensive summary (in Swedish) can be found at www.Cancerfonden.se. It is concluded that radiation therapy plays an increasingly important role in curative and palliative tumour treatment and presents a considerable challenge to research. Several suggestions are made that could improve the possibilities for high-quality radiation therapy research in Sweden.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Turesson, Håkan, et al.
(författare)
-
Prey size selection in piscivorous pikeperch (Stizostedion lucioperca) includes active prey choice
- 2002
-
Ingår i: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 11:4, s. 223-233
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the mechanisms behind prey selection in piscivorous fish is important for our understanding of the dynamics of freshwater systems. Prey selection can involve active predator choice or be a passive process. We experimentally studied size-selectivity in pikeperch, feeding on roach and rudd. When given a choice of different prey sizes, pikeperch selected small prey. Passive selection mechanisms ( encounter rate, capture success and satiation) could not fully explain the pattern of diet choice. Instead, behavioural analysis revealed that the pikeperch actively selected small-sized prey. Optimal foraging theory, predicting that predators will choose prey sizes giving highest energy return per time spent foraging, is assumed to explain active choice. We measured handling times for a range of prey sizes and found that the most profitable sizes were also the chosen ones, both in experiments and in the field. This suggests that pikeperch choose their prey to maximise energy intake per unit time.
|
|
