Locomotory and other movements of the trunk of Bonellia viridis (Echiura, Bonelliidae)

Abstract

Trunk irrigatory and locomotory movements in the echiuran Bonellia viridis consist of peristaltic waves of constriction. Irrigation is by antero-posterior waves. Locomotion in the burrow may be produced in three different ways: (a) by antikinetic, (b) by synkinetic, and (c) by antikinetic and synkinetic waves in strict alternation. The animal can turn in the burrow and pass out of narrow holes. The animal can move by peristaltic waves also outside its burrow. The versatility of locomotory modes is related to its inhabiting ready-made burrows.