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 NEIL, D. M. Articles by MIYAN, J. A. Search for Related Content PubMed Articles by NEIL, D. M. Articles by MIYAN, J. A.

Journal of Experimental Biology 126,157-179 (1986)
Published by Company of Biologists 1986

Phase-Dependent Modulation of Auxiliary Swimmeret Muscle Activity in the Equilibrium Reactions of the Norway Lobster, Nephrops Norvegicus L

DOUGLAS M. NEIL ¹ and JALEEL A. MIYAN ²

¹ Department of Zoology, University of Glasgow, Glasgow G12 8QQ, Scotland
² Department of Zoology, University of Glasgow, Glasgow G12 8QQ, Scotland; Department of Zooogy, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland

1. The activity of swimmeret muscles of the lobster Nephrops norvegicus during beating in the upright and tilted animal has been examined. The responses to tilt are produced primarily by stimulation of the statocysts.

2. The anatomy of the swimmeret muscles is described. Although essentially similar to previous descriptions, important new aspects are presented.

3. The arrangement of the main powerstroke and returnstroke muscle groups in relation to the peg-and-hook articulation of the swimmeret produces a segregation of action, with different muscles contributing progressively to force production.

4. The auxiliary muscles of the basipodite, M9, M10 and M13 act to twist the swimmeret laterally. The auxiliary muscle Ml 1–12–14–15 acts to maintain a rearward powerstroke.

5. The innervation of swimmeret muscles and the location of their motoneurone cell bodies in the abdominal ganglia have been revealed by cobalt staining. There is a clear segregation of powerstroke and returnstroke motoneurones. Intraganglionic fibre tracts as well as four interganglionic fibres are identified.

6. Intracellular studies on the twister muscles show that M9 receives at least three excitatory units, and M10 at least six. No inhibitory activity was ever recorded in these muscles. M9 and the medial bundle of M10 receive tonic excitatory inputs, while the lateral bundle of M10 receives phasic inputs and is normally silent in the absence of lateral beating.

7. In the absence of swimmeret beating, body roll about the long axis induces tonic motor activation of the lateral twister muscles (M9 and M10) and the returnstroke muscles in the swimmerets on the side tilted upwards.

8. When beating occurs it is predominantly in the swimmerets tilted upwards, and there is an entrainment of phasic activity in M9, M10 and M13 to the powerstroke phase of the beats. Tonic units to the returnstroke muscle remain unaffected.

9. The results are discussed with particular reference to the interaction of descending statocyst information with the central pattern generator for swimmeret beating.

Note:
To whom reprint requests should be addressed.

Key words: Crustacea, lobster, swimmeret, equilibrium

Accepted on July 16, 1986