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Journal of Experimental Biology 28,41-50 (1951)
Published by Company of Biologists 1951

The Integration of Activity Cycles in the Behaviour of Arenicola Marina L

G. P. WELLS ¹ and ELINOR B. ALBRECHT ¹

¹ Department of Zoology, University College, London

1. Lugworms were dissected in such a way that the movements of the following parts could be simultaneously recorded: extrovert, body wall from the anterior three segments, body wall from the branchiate segments, tail. The preparations were set up in sea water and tracings were taken for many hours in each case. The preparations typically settled down to give cyclic behaviour patterns, remarkably similar to those which intact worms exhibit under favourable conditions, and in which two components were conspicuous.

2. The first, and most invariable, component is the feeding cycle (f cycle), of period 6-7 min. This rhythm originates in the oesophagus, and is transmitted to the muscles of the proboscis (where it causes outbursts of vigorous contraction) and body wall (where it causes correlated contractions in the first three segments, but periodic inhibition in the branchiate segments).

3. The second component was seen in two-thirds of the experiments. It consists of bursts of vigorous rhythmic activity in the body wall and tail, and can appear after their connexion with the extrovert has been severed. Under exceptional circumstances (exhaustion of the f cycle) it may spread to the extrovert trace. Its period is generally 20-60 min. It is apparently identical with the irrigation-defaecation cycle (i-d cycle) of intact worms.

4. Neither pacemaker directly affects the rhythm of the other. The integration of the activities which they determine probably depends on variation in the extent to which their influences spread through the neuromuscular system. They appear to compete for territory. If they happen to discharge outbursts simultaneously, the i-d pacemaker dominates over most of the body wall, and the f pacemaker over the proboscis and mouth region.

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