QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by SHULTZ, J. W. Search for Related Content PubMed Articles by SHULTZ, J. W.

Journal of Experimental Biology 162,313-329 (1992)
Published by Company of Biologists 1992

Muscle Firing Patterns in two Arachnids using different methods of Propulsive Leg Extension

JEFFREY W. SHULTZ ¹

¹ Department of Zoology, Ohio State University, 1735 Neil Avenue, Columbus, OH 43210, USA; Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA

Activity patterns of six morphologically similar, homologous muscles were recorded from the fourth leg pair in two species of arachnids that use different mechanisms to extend the femur-patella (knee) joint during locomotion. The giant whipscorpion Mastigoproctus giganteus (Uropygi) lacks femur-patella extensor muscles but extends this joint with hydraulic pressure, a mechanism that appears to be phylogenetically primitive in arachnids. The black emperor scorpion Pandinus imperator (Scorpiones) has an unusual muscle that promotes simultaneous extension at the femur-patella joint and distally adjacent patella-tibia joint. Comparison of electromyograms from freely walking animals revealed similarities in muscle firing patterns of the two species, including asymmetrical alternation of trochanter-femur levator and depressor muscles, transfemoral muscle activation during protraction and abrupt termination just prior to levator activation, and persistence of flexor activity during retraction (extension). These results indicate that the apparent evolutionary transition from hydraulic to muscular extension occurred without substantial alteration of several components of the primitive motor programme. It is suggested that the patterns of extension force generated by hydraulic pressure and by bifunctional extensors are similar and that this similarity is associated with conservation of the motorprogramme.

Key words: motor pattern, locomotion, muscle, arthropod, arachnid, evolution, electromyography, Mastigoproctus giganteus, Pandinus imperator

Accepted on August 6, 1991

This article has been cited by other articles:

				A. T. Sensenig and J. W. Shultz Mechanics of cuticular elastic energy storage in leg joints lacking extensor muscles in arachnids J. Exp. Biol., February 15, 2003; 206(4): 771 - 784. [Abstract] [Full Text] [PDF]