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Individual preferences and social interactions determine the aggregation of woodlice.

Devigne C, Broly P, Deneubourg JL - PLoS ONE (2011)

Bottom Line: Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals.Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences.

View Article: PubMed Central - PubMed

Affiliation: Université Lille Nord de France, Lille, France. cedric.devigne@icl-lille.fr

ABSTRACT

Background: The aggregation of woodlice in dark and moist places is considered an adaptation to land life and most studies are focused on its functionality or on the behavioural mechanisms related to the individual's response to abiotic factors. Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.

Methodology/main findings: We present the dynamics of aggregation, not previously described in detail in literature, as being independent of the experimental conditions: homogeneous and heterogeneous environments with identical or different shelters. Indeed whatever these conditions, the aggregation is very quick. In less than 10 minutes more than 50% of woodlice were aggregated in several small groups in the homogeneous environment or under shelters in the heterogeneous environment. After this fast aggregation, woodlice progressively moved into a single aggregate or under one shelter.

Conclusions/significance: Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals. Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences. This inter-attraction can lead to situations that could seem sub-optimal.

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Related in: MedlinePlus

Survival rate of secondary aggregates observed in low, medium and high brightness (respectively, experimental conditions A, B and C).Total number of secondary aggregates observed and means duration of these aggregates are given in the legend of the figure for each experimental condition (means ± SD). Log Rank test showed significant difference between Low brightness and both other situations (p<0.05).
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pone-0017389-g005: Survival rate of secondary aggregates observed in low, medium and high brightness (respectively, experimental conditions A, B and C).Total number of secondary aggregates observed and means duration of these aggregates are given in the legend of the figure for each experimental condition (means ± SD). Log Rank test showed significant difference between Low brightness and both other situations (p<0.05).

Mentions: During the experiments, the evolution of the number of secondary aggregates was similar in every experimental condition: a quick increase was followed by a slow decrease (Figure 4a). Moreover, the average number of woodlice per secondary aggregates was relatively similar, being around 6 woodlice per aggregate whatever the experimental conditions (Figure 4b; differences can be observed between A and C at the beginning but it was not systematic). Hence during the experiments, the number of secondary aggregates was influenced by the aggregation process occurring in woodlice but not the number of woodlice per aggregate. Nevertheless, the evolution of the number of woodlice per aggregate was less regular in high brightness than in other condition. Furthermore, the survival of secondary aggregates was significantly higher in low brightness than in both other situations (Figure 5. Significant difference between low brightness and medium or high brightness, Log Rank test, Log rank statistic  = 5.4, p = 0.02 and 3.9, p = 0.047 for Low vs. Medium and Low vs. High brightness comparisons, respectively). The survival curves of secondary aggregates are well explained by exponential functions in every condition (y = 78.344.e−0.038x, R2 = 0.96; y = 92.199.e−0.076x, R2 = 0.99 and y = 96.197.e−0.084x, R2 = 0.95 for Low, Medium and High brightness). This result showed that the probability of disappearance of secondary aggregates is constant across time.


Individual preferences and social interactions determine the aggregation of woodlice.

Devigne C, Broly P, Deneubourg JL - PLoS ONE (2011)

Survival rate of secondary aggregates observed in low, medium and high brightness (respectively, experimental conditions A, B and C).Total number of secondary aggregates observed and means duration of these aggregates are given in the legend of the figure for each experimental condition (means ± SD). Log Rank test showed significant difference between Low brightness and both other situations (p<0.05).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3045452&req=5

pone-0017389-g005: Survival rate of secondary aggregates observed in low, medium and high brightness (respectively, experimental conditions A, B and C).Total number of secondary aggregates observed and means duration of these aggregates are given in the legend of the figure for each experimental condition (means ± SD). Log Rank test showed significant difference between Low brightness and both other situations (p<0.05).
Mentions: During the experiments, the evolution of the number of secondary aggregates was similar in every experimental condition: a quick increase was followed by a slow decrease (Figure 4a). Moreover, the average number of woodlice per secondary aggregates was relatively similar, being around 6 woodlice per aggregate whatever the experimental conditions (Figure 4b; differences can be observed between A and C at the beginning but it was not systematic). Hence during the experiments, the number of secondary aggregates was influenced by the aggregation process occurring in woodlice but not the number of woodlice per aggregate. Nevertheless, the evolution of the number of woodlice per aggregate was less regular in high brightness than in other condition. Furthermore, the survival of secondary aggregates was significantly higher in low brightness than in both other situations (Figure 5. Significant difference between low brightness and medium or high brightness, Log Rank test, Log rank statistic  = 5.4, p = 0.02 and 3.9, p = 0.047 for Low vs. Medium and Low vs. High brightness comparisons, respectively). The survival curves of secondary aggregates are well explained by exponential functions in every condition (y = 78.344.e−0.038x, R2 = 0.96; y = 92.199.e−0.076x, R2 = 0.99 and y = 96.197.e−0.084x, R2 = 0.95 for Low, Medium and High brightness). This result showed that the probability of disappearance of secondary aggregates is constant across time.

Bottom Line: Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals.Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences.

View Article: PubMed Central - PubMed

Affiliation: Université Lille Nord de France, Lille, France. cedric.devigne@icl-lille.fr

ABSTRACT

Background: The aggregation of woodlice in dark and moist places is considered an adaptation to land life and most studies are focused on its functionality or on the behavioural mechanisms related to the individual's response to abiotic factors. Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics.

Methodology/main findings: We present the dynamics of aggregation, not previously described in detail in literature, as being independent of the experimental conditions: homogeneous and heterogeneous environments with identical or different shelters. Indeed whatever these conditions, the aggregation is very quick. In less than 10 minutes more than 50% of woodlice were aggregated in several small groups in the homogeneous environment or under shelters in the heterogeneous environment. After this fast aggregation, woodlice progressively moved into a single aggregate or under one shelter.

Conclusions/significance: Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals. Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences. This inter-attraction can lead to situations that could seem sub-optimal.

Show MeSH
Related in: MedlinePlus