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Parallel pathways coordinate crawling in the medicinal leech, Hirudo medicinalis
1Department of Biology, University of California San Diego, La Jolla 92093-0357, USA.
Journal of Comparative Physiology. A, Sensory, Neural, and Behavioral Physiology
|June 1, 1995
Summary
Leech crawling behavior persists even without sucker contact or specific nerve connections. Rhythmic cycles depend on head/tail segments and intersegmental pathways, not just midbody sections.
Area of Science:
- Neuroscience
- Animal Behavior
- Biophysics
Background:
- Leech locomotion involves complex coordination of body segments.
- Understanding the neural basis of crawling is crucial for invertebrate neurobiology.
Purpose of the Study:
- To investigate the neural mechanisms underlying leech crawling behavior.
- To determine the role of specific neural structures and body segments in coordinating locomotion.
Main Methods:
- Frame-by-frame video analysis of leeches undergoing various physical manipulations.
- Selective transection and inactivation of body parts and the central nerve cord.
- Assessment of crawling cycle integrity and coordination after experimental interventions.
Main Results:
- Leech crawling cycles continued even when suckers were non-functional.
- Transection of Faivre's nerve disrupted whole-body shortening reflexes but not crawling.
- Complete transection of intersegmental connectives led to loss of coordination.
- Crawling was maintained in body segments containing head/tail plus adjacent midbody segments.
- Midbody segments alone did not support crawling.
Conclusions:
- Sucker engagement is not essential for the leech crawling cycle.
- Distinct neural pathways mediate whole-body shortening and crawling contraction phases.
- Intersegmental connectives are vital for coordinated leech locomotion.
- Head and tail ganglia play a role in initiating and switching crawling phases.
- A model involving intersegmental pathways and central pattern generators explains leech crawling.