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Fig. 3 | Frontiers in Zoology

Fig. 3

From: Skeletal regeneration in the brittle star Amphiura filiformis

Fig. 3

Histological sections of regenerating arms at stages 3, 4 and 5. Sagittal and transverse paraffin sections at stage 3 (A and A”), and sagittal sections of stages 4 (B), and 5 (C) stained with Milligan’s trichrome technique. Collagen stained cyan, all cells labeled pink/magenta. Red dashed line indicates amputation plane. A) The three regenerating axial structures are enveloped by the dermal layer (arrow) and the new epidermis. A') Detail of A showing mesenchymal cells at the level of the aboral dermal layer (arrow) covered by the new epidermis with its cuticle (asterisk). A”) Transverse section of a stage 3 regenerate showing the dermal layer (arrow), developing radial nerve, radial water canal and aboral coelomic cavity. B) The stage 4 regenerate is longer and the radial water canal shows the first signs of podia regeneration. B') Detail of B showing the developing podia (dotted line). B'') Detail of B showing the scattered mesenchymal cells in the aboral dermal layer (arrow). C) Further development and differentiation of the three axial structures at stage 5. C') Detail of developing podia (dotted line). A - aboral, ACC - aboral coelomic cavity, CT - connective tissue, D - distal, E - epidermis, ES - ectoneural sinus, HS - hyponeural sinus, L - left, N - radial nerve, O - oral, P - proximal, Po - developing podia, RWC - radial water canal, R - right, SS - sagittal section, TS - transverse section

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