Article

# Modeling Vortex Swarming In Daphnia

ETH Zurich, Chair of Systems Design, Kreuzplatz 5, CH-8032 Zurich, Switzerland.
(Impact Factor: 1.39). 03/2007; 69(2):539-62. DOI: 10.1007/s11538-006-9135-3
Source: PubMed

ABSTRACT

Based on experimental observations in Daphnia, we introduce an agent-based model for the motion of single and swarms of animals. Each agent is described by a stochastic equation that also considers the conditions for active biological motion. An environmental potential further reflects local conditions for Daphnia, such as attraction to light sources. This model is sufficient to describe the observed cycling behavior of single Daphnia. To simulate vortex swarming of many Daphnia, i.e. the collective rotation of the swarm in one direction, we extend the model by considering avoidance of collisions. Two different ansatzes to model such a behavior are developed and compared. By means of computer simulations of a multi-agent system we show that local avoidance - as a special form of asymmetric repulsion between animals - leads to the emergence of a vortex swarm. The transition from uncorrelated rotation of single agents to the vortex swarming as a function of the swarm size is investigated. Eventually, some evidence of avoidance behavior in Daphnia is provided by comparing experimental and simulation results for two animals.

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Available from: Frank Schweitzer, Sep 30, 2015
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• "The high concentration of nutrients attracts individuals and repulsive forces between individuals, as well as the turning behaviour towards high nutrient concentrations (see fi,2(t) above), cause the aggregation and circular motion of individuals in our simulations. Previous theoretical work has already demonstrated that self-propelled individuals readily form vortices around attractive potentials, even with minimal interactions between individuals [26], [31]. This result serves to illustrate that non-homogeneous nutrient distributions can affect the movement dynamics and we further discuss this below. "
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