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Systems That Control the Burrowing Behaviour of a Sea Anemone
1 Department of Molecular and Cellular Biology, The University of Arizona Tucson, AZ 85721, USA
The sand-dwelling sea anemone, Phyllactis concinnata, buries itself by attaching sand grains to the lower column as this is bent under the anemone by a travelling peristaltic wave. Some of the sand is then released as the column expands laterally. Once buried, the anemone increases in length over a period of several hours until the pedal disc finally attaches to a buried shell. Burrowing is controlled by bursts of pulses generated by the through-conducting nerve net. These pulses produce column shortening and peristalsis. Regular intervals between pulses and between bursts suggest that pacemakers are driving the nerve net. Pulse patterns are modified after sand has surrounded the column and when the pedal disc touches hard substratum. A second conducting system (the SS2) can, under specific experimental conditions, respond to mechanical and chemical stimuli and inhibit nerve net discharge, but its function during burrowing is not known, even though it produces a distinctive pattern of pulses. After the column has been buried, an anemone may contract spontaneously and rapidly. Two other types of behaviour, pharynx eversion and antiperistaltic behaviour (crawling), usually precede burrowing and each is associated with its own characteristic pattern of pulses.
Key words: sea anemone, burrowing, nerve net
Accepted on September 2, 1987
