Abstract
The marine nudibranch Tritonia diomedea crawls using its ciliated foot surface as the sole means of propulsion. Turning while crawling involves raising a small portion of the lateral foot margin on the side of the turn. The cilia in the lifted area no longer contribute to propulsion, and this asymmetry in thrust turns the animal towards the lifted side. Neurons located in the pedal ganglia of the brain contribute to these foot margin contractions. T. diomedea has a natural tendency to turn upstream (rheotaxis), and pedal flexion neuron Pedal 3 elicits foot margin lift and receives modulatory input from flow receptors. To assess the contribution of this single cell in turning behavior, two fine wires were glued to the surface of the brain over left and right Pedal 3. We determined that Pedal 3 activity is correlated with subsequent ipsilateral turns, preceding the lift of the foot margin and the change in orientation by a consistent interval. Both Pedal 3 cells show synchronous bursts of activity, and the firing frequency of the ipsilateral Pedal 3 increased before turns were observed to that side. Stimulation of the electrode over Pedal 3 proved sufficient to elicit an ipsilateral turn in Tritonia.
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Abbreviations
- Pd:
-
Pedal
- LPd3:
-
Left pedal neuron 3
- RPd3:
-
Right pedal neuron 3
- CPG:
-
Central pattern generator
- DSI:
-
Dorsal swim interneuron.
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Acknowledgements
Thanks to the faculty and staff of the University of Central Arkansas and the Friday Harbor Laboratories. Financial support was provided by the University of Central Arkansas, the Arkansas Science and Technology Authority, and a Libbie Hyman Memorial Scholarship (to RR). We also gratefully acknowledge the technical assistance of Lauw Klaassen, Charlie Ratcliffe, Allan Roisen, Martin Erwin, Elizabeth Murray, and Russell Wyeth. Thanks to Shaun Cain, Beth Moore, Owen Woodward, Russell Wyeth, and Living Elements for providing slugs, and to two anonymous reviewers for suggested improvements to the manuscript. These experiments comply with the “Principles of animal care”, publication No. 86–23, revised 1985 of the National Institute of Health.
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Redondo, R.L., Murray, J.A. Pedal neuron 3 serves a significant role in effecting turning during crawling by the marine slug Tritonia diomedea (Bergh). J Comp Physiol A 191, 435–444 (2005). https://doi.org/10.1007/s00359-005-0604-1
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DOI: https://doi.org/10.1007/s00359-005-0604-1