[Types of locomotion in Ophiuroidea]

Locomotor movements of two species of ophiura from the Sea of Japan: Ophiura sarsi vadicola Djakonov and Amphipholis kochii Lütken, were filmed. Ophiura sarsi moves by means of two symmetric pairs of arms which perform rhythmical rowing movements, the fifth arm is passive and directed backwards. Animals of this species do not use tube feet in locomotion. In Amphipholis kochii, three main modes of locomotor movements were found. (1) "Breast stroke" in which two symmetric side arms periodically move forwards, and then push forwards the body and three other arms. In this mode, one arm (leading) is directed forwards, while two others backwards. When the side arms move-forwards or backwards, a wave of successive flexions and extensions propagates along the arm segments. (2) "Pushing" by means of the hind arm and "pulling" with the help of the leading arm. (3) Locomotion by means of the tube feet which perform stepping movements. These three modes of locomotion are observed either separately or in various combinations with each other. In (1) and (2) modes of locomotion the tube feet perform also the coupling of the active arms with the ground which is necessary for the animal movement.