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 Google Scholar Google Scholar Articles by Abby-Kalio, N. J. Articles by Warner, G. F. Search for Related Content PubMed Articles by Abby-Kalio, N. J. Articles by Warner, G. F.

Journal of Experimental Biology 125,309-318 (1986)
Published by Company of Biologists 1986

Adduction Levers and Adductor Muscle Function in the Mandibular System of the Shore Crab Carcinus Maenas

N. J. Abby-Kalio ¹ and G. F. Warner ²

¹ Department of Pure and Applied Zoology, University of Reading, Whiteknights, PO Box 228, Reading, RG6 2AJ, UK: Department of Biological Sciences, University of Science and Technology, P.M.B. 5080, Port Harcourt, Nigeria.
² Department of Pure and Applied Zoology, University of Reading, Whiteknights, PO Box 228, Reading, RG6 2AJ, UK

The lever systems, and structure and function of the adductor muscles, of the mandibles of large male Carcinus tnaenas (L.) were investigated. The functional mechanical advantage (FMA) of the external adductor muscles, measured at the middle of the biting edge of the mandible, was 1.53 ± 0.01; the ideal mechanical advantage (IMA), calculated from measured lever lengths, was 1.78±0.03 (mean±S.E.). The FMA of the internal adductor muscles was 0.53±0.01 and the IMA was 0.62±0.02.

When slowly loaded, the external adductor system broke at 3.09±0.16 N; when rapidly loaded, the system broke at 7.16±0.79 N. Short duration loading at 2.0 N or more was found to result in histologically detectable damage at the pivot. When slowly loaded, the internal adductor system broke at 0.68±0.05 N. When a load of 0.39 N was applied to the internal adductor system, the failure point on slow loading of the external adductor system was not significantly increased.

The mean maximum force of contraction of the external adductor muscles on electrical stimulation was 0.98±0.03 N, with a stress of 627kNm^-2 in the fibres. The internal adductors contracted with a mean maximum force of 0.33±0.01 N. The total maximum bite force is therefore about 3.3 N, only 10% being contributed by the internal adductors. The safety factor of both internal and external systems is about 2.

The mean sarcomere length of half-contracted fibres of the external adductor muscles was 11.62±0.11 µm.

Key words: biomechanics, Brachyura, Carcinus, Crustacea, feeding, leverage, muscle, mandibles, safety factors, sarcomeres.

Accepted on May 9, 1986