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

This Article Full Text (PDF) References 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 Similar articles in PubMed 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 Faulkes, Z. Articles by Paul, D. H. Search for Related Content PubMed PubMed Citation Articles by Faulkes, Z. Articles by Paul, D. H.

Journal of Experimental Biology, Vol 201, Issue 14 2139-2149, Copyright © 1998 by Company of Biologists

JOURNAL ARTICLES

Digging in sand crabs: coordination of joints in individual legs

Z Faulkes and DH Paul
Department of Biology, University of Victoria, PO Box 3020, Victoria, British Columbia, Canada V8W 3N5. dhp@uvvm.uvic.ca.

Sand crabs use their multi-jointed legs to dig into sand. Combined movement and electromyogram (EMG) analyses showed that the pattern of intra-leg coordination in the legs of two sand crabs of different families (Blepharipoda occidentalis and Emerita analoga) is similar in legs 2 and 3, but very different in leg 4. For example, the sequence of proximal joint movements in legs 2 and 3 is elevation, retraction, depression and protraction (similar to backward walking in most decapods), but the sequence of proximal joint movements in leg 4 is elevation, protraction, retraction and depression (similar to forward walking). The synergies are the same during leg movements in sea water and in sand, suggesting that the same motor programme is used in both situations. At the transition from sea water into sand, however, both the frequency and amplitude of the EMG potentials increase, and the phasing of the motor output to leg 2 (and presumably leg 3) changes from proportional (both power and return strokes co-vary with period) to return stroke constant (power strokes co-vary much more with period than do return strokes). The motor output to leg 4 remains intermediate between proportional and return stroke constant in sea water and in sand. On the basis of the segmental specialisation of the motor patterns for the legs, we hypothesize that sand crab digging may be an evolutionary mosaic of disparate ancestral locomotor behaviours.

This article has been cited by other articles:

				Y. Manor, A. Bose,, V. Booth, and F. Nadim, Contribution of Synaptic Depression to Phase Maintenance in a Model Rhythmic Network J Neurophysiol, November 1, 2003; 90(5): 3513 - 3528. [Abstract] [Full Text] [PDF]