| 1. |
|
|
| 2. |
- Adameyko, I, et al.
(författare)
-
Sox2 and Mitf cross-regulatory interactions consolidate progenitor and melanocyte lineages in the cranial neural crest
- 2012
-
Ingår i: Development (Cambridge, England). - : The Company of Biologists. - 1477-9129 .- 0950-1991. ; 139:2, s. 397-410
-
Tidskriftsartikel (refereegranskat)abstract
- The cellular origin and molecular mechanisms regulating pigmentation of head and neck are largely unknown. Melanocyte specification is controlled by the transcriptional activity of Mitf, but no general logic has emerged to explain how Mitf and progenitor transcriptional activities consolidate melanocyte and progenitor cell fates. We show that cranial melanocytes arise from at least two different cellular sources: initially from nerve-associated Schwann cell precursors (SCPs) and later from a cellular source that is independent of nerves. Unlike the midbrain-hindbrain cluster from which melanoblasts arise independently of nerves, a large center of melanocytes in and around cranial nerves IX-X is derived from SCPs, as shown by genetic cell-lineage tracing and analysis of ErbB3-null mutant mice. Conditional gain- and loss-of-function experiments show genetically that cell fates in the neural crest involve both the SRY transcription factor Sox2 and Mitf, which consolidate an SCP progenitor or melanocyte fate by cross-regulatory interactions. A gradual downregulation of Sox2 in progenitors during development permits the differentiation of both neural crest- and SCP-derived progenitors into melanocytes, and an initial small pool of nerve-associated melanoblasts expands in number and disperses under the control of endothelin receptor B (Ednrb) and Wnt5a signaling.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Nicolis, C, et al.
(författare)
-
Propagation of extremes in space
- 2009
-
Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 80:2, s. 026201-
-
Tidskriftsartikel (refereegranskat)abstract
- The propagation of extreme events in space is analyzed for a class of dynamical systems giving rise to spatiotemporal chaos. It is shown that this process can be mapped into a generalized random walk, whereby the mean square displacement increases linearly in time and there is a nonvanishing probability for jumps beyond first neighbors. The relative roles of the local dynamics and of the spatial coupling are identified.
|
|
| 6. |
- Nicolis, S. C., et al.
(författare)
-
Extreme events in bimodal systems
- 2008
-
Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 78:3, s. 036222-
-
Tidskriftsartikel (refereegranskat)abstract
- The extreme value statistics of systems possessing a two-hump probability density of the relevant variable, in which the left peak is more pronounced than the right one, is studied. It is shown that systems of this type display a nontrivial transient behavior in the form of anomalous fluctuations around the mean, for certain (finite) ranges of observational time windows. The results are illustrated on independent identically distributed random variables, systems possessing two locally stable states and subjected to additive white noise, and dynamical systems in the regime of deterministic chaos.
|
|
| 7. |
- Arganda, S., et al.
(författare)
-
Collective choice in ants : The role of protein and carbohydrates ratios
- 2014
-
Ingår i: Journal of insect physiology. - : Elsevier BV. - 0022-1910 .- 1879-1611. ; 69, s. 19-26
-
Tidskriftsartikel (refereegranskat)abstract
- In a foraging context, social insects make collective decisions from individuals responding to local information. When faced with foods varying in quality, ants are known to be able to select the best food source using pheromone trails. Until now, studies investigating collective decisions have focused on single nutrients, mostly carbohydrates. In the environment, the foods available are a complex mixture and are composed of various nutrients, available in different forms. In this paper, we explore the effect of protein to carbohydrate ratio on ants' ability to detect and choose between foods with different protein characteristics (free amino acids or whole proteins). In a two-choice set up, Argentine ants Linepithema humile were presented with two artificial foods containing either whole protein or amino acids in two different dietary conditions: high protein food or high carbohydrate food. At the collective level, when ants were faced with high carbohydrate foods, they did not show a preference between free amino acids or whole proteins, while a preference for free amino acids emerged when choosing between high protein foods. At the individual level, the probability of feeding was higher for high carbohydrates food and for foods containing free amino acids. Two mathematical models were developed to evaluate the importance of feeding probability in collective food selection. A first model in which a forager deposits pheromone only after feeding, and a second model in which a forager always deposits pheromone, but with greater intensity after feeding. Both models were able to predict free amino acid selection, however the second one was better able to reproduce the experimental results suggesting that modulating trail strength according to feeding probability is likely the mechanism explaining amino acid preference at a collective level in Argentine ants.
|
|
| 8. |
|
|
| 9. |
- Dussutour, A, et al.
(författare)
-
Noise improves collective decision-making by ants in dynamic environments
- 2009
-
Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 276:1677, s. 4353-4361
-
Tidskriftsartikel (refereegranskat)abstract
- Recruitment via pheromone trails by ants is arguably one of the best-studied examples of self-organization in animal societies. Yet it is still unclear if and how trail recruitment allows a colony to adapt to changes in its foraging environment. We study foraging decisions by colonies of the ant Pheidole megacephala under dynamic conditions. Our experiments show that P. megacephala, unlike many other mass recruiting species, can make a collective decision for the better of two food sources even when the environment changes dynamically. We developed a stochastic differential equation model that explains our data qualitatively and quantitatively. Analysing this model reveals that both deterministic and stochastic effects (noise) work together to allow colonies to efficiently track changes in the environment. Our study thus suggests that a certain level of noise is not a disturbance in self-organized decision-making but rather serves an important functional role.
|
|
| 10. |
- Dussutour, A., et al.
(författare)
-
The role of multiple pheromones in food recruitment by ants
- 2009
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 212:15, s. 2337-2348
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate the foraging activity of an invasive ant species, the big headed ant Pheidole megacephala. We establish that the ants' behavior is consistent with the use of two different pheromone signals, both of which recruit nestmates. Our experiments suggest that during exploration the ants deposit a long-lasting pheromone that elicits a weak recruitment of nestmates, while when exploiting food the ants deposit a shorter lasting pheromone eliciting a much stronger recruitment. We further investigate experimentally the role of these pheromones under both static and dynamic conditions and develop a mathematical model based on the hypothesis that exploration locally enhances exploitation, while exploitation locally suppresses exploration. The model and the experiments indicate that exploratory pheromone allows the colony to more quickly mobilize foragers when food is discovered. Furthermore, the combination of two pheromones allows colonies to track changing foraging conditions more effectively than would a single pheromone. In addition to the already known causes for the ecological success of invasive ant species, our study suggests that their opportunistic strategy of rapid food discovery and ability to react to changes in the environment may have strongly contributed to their dominance over native species.
|
|
