Giant nerve fibers in annelids

Les Watling watling at
Fri Mar 29 17:01:06 EST 2002

A check of my animal physiology books shows a top nerve transmission speed 
of 100 m/sec in a shrimp nerve fiber.  Giant nerve fibers in the polychaete 
Myxicola conduct at about 20 m/sec.  Lumbricus is listed at 11.3 m/sec in 
one reference and 30-38 m/sec in another.  It seems the important variables 
are diameter and myelination.  Myxicola has the former but not the latter, 
whereas oligochaetes apparently have large diameter axons with a 
myelin-like outer sheath.  Check Prosser,  Comparative Animal Physiology, 
volume on Neural and Integrative Animal Physiology.

At 08:45 PM 3/29/2002 +0000, James Mahaffy wrote:
>I am a zoology teacher at Dordt College and was talking about annelids
>last lecture.  I ran across information in the second edition (1977) of
>Edwards and Lofty's Biology of earthworms (p. 105) that I think may be a
>typo.  They say that giant nerve fibers in annelids (I assume Lumbricus
>terrestris) transmit impulses at 600 meters per second.  Somehow that
>seems to be high and I wonder if it was a typo. I did a bit of researching
>other sources I have available on nerve conduction and got 35 meters
>per second.  

Les Watling
Professor of Oceanography and
Pew Fellow in Marine Conservation
Darling Marine Center
University of Maine
Walpole, ME 04573

Phone 207-563-3146 x248
Fax  207-563-3119

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