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First published online July 20, 2006
Journal of Experimental Biology 209, 2839-2846 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02337

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Like a `rolling stone': quantitative analysis of the body movement and skeletal dynamics of the sponge Tethya wilhelma

Michael Nickel

Department of Zoology, Biological Institute, Stuttgart University, 70550 Stuttgart, Germany

View larger version (88K): [in a new window]   Fig. 1. The sponge Tethya wilhelma (A) on natural substrate, recorded from above, (B) a glass plate, recorded from below, with indicated directional change, and (C) on a plastic substrate, recorded from the side. Black dots mark the sponge centre at t=0 min, white dots and corresponding outlines mark the location of the sponge body after the indicated times (min). Bars=5 mm; indicated axes correspond to Fig. 2. The complete time-lapse series are displayed in supplementary material Movies S1-S3.

View larger version (32K): [in a new window]   Fig. 2. Movement of the central body trace point of T. wilhelma. (A) Sub-basal view, giving lateral movements in x- and y-direction, corresponding to Fig. 1B and supplementary material Movie S2; note the slight shifts due to contraction. (B) Lateral view, giving movements in the x-direction and body shifts in the z-direction based on contraction, corresponding to Fig. 1C and supplementary material Movie S3. Time points are indicated in grey to allow comparison to supplementary material Movies S2 and S3.

View larger version (26K): [in a new window]   Fig. 3. (A) Lateral movement of T. wilhelma on natural substrate (Fig. 1A), displaying three movement phases; (B) Contraction (projected body area) and lateral movement of T. wilhelma on a glass plate (Fig. 1B), with three distinct movement phases; (C) Contraction (projected body area) and lateral movement of T. wilhelma on a plastic plate (Fig. 1C), with even movement. For average contraction speeds and more details, refer to text.

View larger version (137K): [in a new window]   Fig. 4. Changes of angles based on skeletal structures in T. wilhelma. (A,B) Rotation on baso-apical axis: (A) 4875 min, (B) 6945 min. (C,D) Rotation on lateral axis: (C) 0 min, (D) 1473 min; Experimental times in correlation to time-lapse recordings given in supplementary material Movies S2 and S3; TP, central trace point; T1/T2, marker points. : angle between vertical image axis and line TP-T1; ß, angle between vertical image axis and line TP-T2; internal angle between lines TP-T1 and TP-T2. Bars=5 mm. For details on measured angles refer to text and see Fig. 5 and supplementary material Movies S4 and S5.

View larger version (51K): [in a new window]   Fig. 5. Changes of angles based on skeletal structures in T. wilhelma over time in relation to body contraction (projected body area). (A) Rotation on baso-apical axis; (B) rotation on lateral axis. Angles are labelled as defined in Fig. 4. For details refer to text and compare supplementary material Movies S4 and S5.