Nickel, M. 2006. Like a 'rolling stone': quantitative analysis of the body movement and skeletal dynamics of the sponge Tethya wilhelma. Journal of Experimental Biology 209:2839-2846.

How do sponges that have no muscle and no central nervous system locomote and do the surface they're on effect the movement? The sponge T. wilhelma helps us investigate sponge movement because of its unique movement and body contractions.

Tethya sp. have been reported as the sponges with the most cases of movement. Previous studies have shown that the movement of sponges is based on organizational plasticity, a rearrangement of their skeleton and body. Also, a past study suggested that the movement of the genus Tethya was due to the contraction of extensions. This was later disproved by other authors.

Nickel placed different Tethya sp. on different surfaces and tracked their movement using digital time-lapse imaging. It was shown that T. wilhelma does not have amoeboid-like movement but instead rotates its skeleton to produce a rolling movement.

Nickel concludes that T. wilhelma moves like a 'rolling stone' in that it moves only when conditions are unfavorable due to the fact that the movement has direction to it. It is also shown that movement is almost completely upon the baso-apical axis. The surface the sponge was placed on did not have a significant effect on the movement.

(200 words)

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(posted Mar. 24 2009)