How do starfish move?

Answer 1

feet

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T2K-4H8MP53-1&_user=1515455&_coverDate=11%2F30%2F2005&_rdoc=1&_fmt=full&_orig=search&_cdi=4921&_sort=d&_docanchor=&view=c&_acct=C000053262&_version=1&_urlVersion=0&_userid=1515455&md5=5caa67d65840945d332fac07a97a3202#secx9

== Tube feet activities of walking individuals of A. pectinifera with respect to speed of movements and arm orientations were observed to estimate their contributions to the obstacle avoidance behaviors. The experimental tank had white acrylic walls and a transparent bottom and measured 35 cm in both width and depth, and 15 cm in height. The tank was filled with seawater to a depth of 5 cm and was illuminated using two 10-W fluorescent lamps so that there was no shade inside; this was because shade may elicit directed movements of starfish (e.g., Yoshida and Ohtsuki, 1968). Furthermore, there was no source of odor that may attract the starfish, allowing us to observe tube feet activities without a directive stimulus. A specimen was put in the center of the tank and allowed to move freely. A CCD camera was set beneath the tank to record tube feet movements. To obtain clear images of the tube feet, the camera frame was set to a rather small area measuring 21.5 cm × 16.5 cm. Thus, A. pectinifera would move out of the frame within a few minutes and long data sequences could not be obtained. When a starfish walked to the end of the tank, it was replaced at the starting position by hand. When the experimenter touched the specimen, special care was taken not to handle the arms, because touching them may cause retraction of the tube feet, which may eventually cause a direction change in the specimen's movement. Still images with a resolution of 640 × 480 were captured from the videotape recorded at a rate of four frames per second. As captured images divided an area of 21.5 cm × 16.5 cm into 640 × 480 pixels, the minimum object size was approximately 0.34 mm. This resolution was not very fine, but was sufficient to allow detection of the tube feet, which are approximately 1.2 mm in diameter. The sampling rate was also sufficient to allow observation of movements of A. pectinifera, although movement itself was not analyzed in the present study. From each image, the positions of the tips of arms and the mouth located in the center of the disk were determined. It is possible to calculate the approximate orientation of the rays from these data. The number of tube feet was counted to measure locomotion activity. When an A. pectinifera remains still and does not move, the tube feet retreat into the crevices under the arms and the number of detectable tube feet is relatively small. In contrast, when activity of A. pectinifera is rather high and the starfish moves rapidly, many tube feet can be observed. == When an individual was placed in the center of the observation tank, it sometimes became inactive with the tube feet retreated into the crevices under the arms, which makes it difficult to observe all of the tube feet. On the other hand, when a starfish is in a highly activated state, all the tube feet are moving and could be counted easily. Thus, the number of tube feet observed, indicating the number of working tube feet, can be used as an index of the activity of the starfish. When the tube feet show synchronous movements, the starfish shows relatively smooth locomotion (Koh and Lane, 1998 B.C.A. Koh and D.J.W. Lane, Locomotory coordination and the podia-ampulla system in Stellaster equestris(Asteroidea: Goniasteridae). In: R. Mooi and M. Telford, Editors, Echinoderms: San Francisco, Belkema, Rotterdam (1998), pp. 259-263.Koh and Lane, 1998). However, some arms may have more difficulty in maintaining synchrony, because the tube feet are arranged in two lines along the crevices running along the arms. If a tube foot steps toward the tip of arm or the mouth, i.e., along the ray, it will collide more frequently with other tube feet. In contrast, if a tube foot moves perpendicular to the ray, it has the least chance of collision and it will make a maximum contribution to movement of the arm.

Answer 2

starfish move using a water vascular system which sucks water through to their tubed feet which means their tubed feet can suck on to things. they then shimmy like a caterpillar