Fiddler crab burrow defence: A robot simulation
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1
University of Edinburgh, Informatics, United Kingdom
Fiddler crabs, as central place foragers, are an ideal organism for studying how the navigation and visual system combine during behaviours such as resource defence. It is known that fiddler crabs are able to perform highly accurate navigation using path integration [1,2] and their visual system exploits the relatively flat, simple environment in which they live [3]. However, exactly how and what aspects of these two systems combine in the decision to respond to threats is still unclear although several theories, both mathematical and neural, have been hypothesised. I will present a robot simulation to explore potential models of burrow defence in fiddler crabs.
The theory I have focused on thus far is that put forth by Hemmi and Zeil [4] who explored such behaviour in the species Uca. vomeris. It was argued that these crabs are able to determine distance of an object from itself based on its elevation on the retina. In other words the further down the retina an object is seen the closer it is. It was also found that the crab’s response to threats is highly dependent on their home vector produced by the navigation system, i.e. the further from the burrow the sooner they will respond to a potential threat. Hemmi and Zeil hypothesized that a retinal filter which maps distances to the burrow across the retina, mediated by the output of the navigation system, could be a potential simple model for burrow defence.
Currently the simulation uses geometry, based on a home vector and retinal elevation, to create such a filter on a camera image. This filter defines the area in the environment which is closer to the burrow than the crab itself as seen on the retina. Experiments involved a robot approaching the “burrow” from different directions while the camera simulating the crab remained stationary at a certain distance from the “burrow”. The trajectories of the approaching robot were retrieved up until the point at which the simulation decided it should respond to the threat, in other words, when the robot was seen to have entered into the retinal filter. The results so far show that the simulated crab reacts when the threat comes within a distance of their burrow approximately equal to their home vector. The next step considers a neural implementation of such a filter; simulating motion detector neurons as input to distance neurons. These distance neurons are sensitive to certain distances to the burrow and the current distance neuron(s) to be used are selected by the output of the navigation system. This simulation will either give support to Hemmi and Zeil's theory or show that other possible models may need to be considered and explored.
Acknowledgements
Barbara Webb - University of Edinburgh (1st supervisor)
Jon Barnes - University of Glasgow (2nd supervisor)
References
[1] Zeil, J. (1998). Homing in fiddler crabs (Uca lactea annulipes and Uca vomeris: Ocypodidae). Journal of Comparative Physiology A Sensory Neural and Behavioral Physiology, 183(3), 367-377. doi:10.1007/s003590050263
[2] Layne, J. E. (2003). Mechanisms of homing in the fiddler crab Uca rapax 1. Spatial and temporal characteristics of a system of small-scale navigation. Journal of Experimental Biology, 206(24), 4413-4423. doi:10.1242/jeb.00660
[3] Zeil, J., & Hemmi, J. M. (2006). The visual ecology of fiddler crabs. Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology, 192(1), 1-25. doi:10.1007/s00359-005-0048-7
[4] Hemmi, J. M. & Zeil, J. (2003). Burrow surveillance in fiddler crabs II. The sensory cues. Journal of Experimental Biology, 206(22), 3951-3961. doi:10.1242/jeb.00636
Keywords:
Burrow defence,
fiddler crab,
navigation,
Robot Simulation,
Visual behaviour
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for student poster award)
Topic:
Sensory: Vision
Citation:
Gardner
C
(2012). Fiddler crab burrow defence: A robot simulation.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00290
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Ms. Christine Gardner, University of Edinburgh, Informatics, Edinburgh, EH8 9AB, United Kingdom, chrissie.gardner@gmail.com