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First published online September 19, 2006
Journal of Experimental Biology 209, 3873-3881 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02445

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Growth or differentiation? Adaptive regeneration in the brittlestar Amphiura filiformis

Samuel Dupont^* and Michael C. Thorndyke

Kristineberg Marine Station, 566 Kristineberg, 45034 Fiskebäckskil, Sweden

View larger version (13K): [in a new window]   Fig. 1. Amphiura filiformis. Diagram of the whole animal experiment; LL, length lost, which ranged between 5 and 60 mm.

View larger version (11K): [in a new window]   Fig. 2. Amphiura filiformis. Diagram of the explant experiment; LL, length lost, which ranged between15 and 65 mm. All scale bars represent 10 mm.

View larger version (90K): [in a new window]   Fig. 3. Regenerating arm of Amphiura filiformis. The new arm has extended in length and is clearly distinguishable from the older stump. The demarcation between the proximal differentiated part (with ossicles, podia and spines) and the distal undifferentiated part is indicated by a dotted line. DL, differentiated length (in mm); RL, regenerated length (in mm).

View larger version (18K): [in a new window]   Fig. 4. Non-regenerating arm of Amphiura filiformis. Relationship between the disc diameter (in mm) and the maximal length (in mm) of the intact arm before amputation.

View larger version (14K): [in a new window]   Fig. 5. Relationship between the position (number of segments from distal to proximal) and the length (in mm) of a segment on a non-regenerating arm.

View larger version (14K): [in a new window]   Fig. 6. Relationship between the length lost (LL; in mm) and regeneration rate (RR; in mm week-1).

View larger version (13K): [in a new window]   Fig. 7. Relationship between the length lost (LL; in mm) and the differentiation rate (DR1; in mm week-1).

View larger version (13K): [in a new window]   Fig. 8. Relationship between the length lost (LL; in mm) and the differentiation rate (DR2; in % week-1).

View larger version (21K): [in a new window]   Fig. 9. Relationship between the size of the regenerate (in mm) and its differentiation index (DI; in %) for different lengths lost (LL; ranged between 5 and 60 mm).

View larger version (63K): [in a new window]   Fig. 10. Comparison of regenerate at different times of regeneration and two different amputation levels (5 and 50 mm; measured as length lost; LL). The differentiation index (DI; in %) is given below each image. ap, amputation plane. The first difference was observed on day 6, when the blastema was longer for the arm amputated at 50 mm from the tip. After 12 days, important differences in both size and differentiation were observed. The arms cut at 5 mm from the tip regenerated a smaller arm (1.2 mm), which had already started to differentiate complete segments with spines and tube feet while arms cut at 50 mm from the tip regenerated a longer arm (2 mm) but no complete segments were formed. These differences were amplified after 19 days. The regenerate was three times longer for the arm cut at 50 mm from the tip but less differentiated (DI of 45% versus 70%) than the one cut at 5 mm from the tip.

View larger version (13K): [in a new window]   Fig. 11. Relationship between the length lost (LL; in mm) and the regeneration rate (RR; in mm week-1) on growing explants.