Phase Co-Ordination in the Cardiac and Ventilatory Rhythms of the Lobster <i>Homarus Americanus</i>

Abstract

ABSTRACT Relative co-ordination is demonstrated between the rhythms of the right and left scaphognathites (SG) and between the heart and either right or left SG or both simultaneously. The co-ordination between these rhythms results from mutual phasedependent alteration of the period lengths as demonstrated by the phaseresponse curves for the interactions. The standard deviation of the SG period lengths is an inverse linear function of the percentage coupling between the two SGs (r = 0·76; P &amp;lt; 0·01). The right SG motor output may show relative co-ordination with respect to a sinusoidal, dorso-ventral movement applied along the radial axis of that appendage. This is taken to indicate that sensory reafference resulting from the interplay between the applied and intended movements can alter the SG rhythm depending upon the relative phasing of the two movements. The effects of sensory reafference are therefore not merely tonic as has been believed until now. Cautery of the right oval organ, a major phasic mechanoreceptor of the SG, has no significant influence on any of the above relationships. The significance of this and of the widespread occurrence of relative co-ordination between rhythmic activities is discussed.