Fig. 3

Fig. 3 Regenerate of nonbifurcating ray R1 can form bifurcation when grafted in the interray tissue between bifurcating rays R9. (A) Detail of the R1 fragment 30 days after proximal grafting between the R9 rays. (B) Hematoxilin–eosin staining of a cross-section of a fin at the level of the graft (h), 30 days after grafting. e, epidermis; h, hemiray. (C) Picrosirius–hematoxilin staining of a cross-section of the graft showing that the epidermis of R1 (arrow) is still attached to the R1 lepidotrichia (l) 2 days after grafting. (D) Distal region of a segmented regenerate growing out of the fin (arrow) 1 month postoperation. (E) Transverse section of one hemiray of an R1–I9 heterotopical graft which has regenerated inside the interray tissue. The interray epidermis covering the graft (arrowhead) becomes thinner than the normal interray epidermis (asterisk) and resembles the epidermis of a ray. (F) Transverse section through the blastema of a 4 days regenerate developing from the grafted piece of R1 that was labeled with DiI prior grafting. DiI labeling is restricted to the blastema cells (b). In contrast, epithelial cells (e) and interray tissue are not labeled. (G). White cells (arrows) are restricted to the distal portion of the lateral long rays (R1–R4) of each lobe of the tail fin. After mounting the fins, these cells become orange and are easily distinguished from the more abundant melanocytes, which are black (arrowhead). R1 and R2, original first and second rays. (H) Detail of a regenerate obtained following amputation at the level of the R1–I9 graft. The regenerate is surrounded by the central interray tissue (I9) and presents white cells (arrow) characteristic of R1 and melanocytes (arrowhead), which are found in most of rays. (I) Detail of the distal margin a regenerated R1–I9 heterotopical graft. The graft regenerate shows a bifurcation and segmentation pattern similar to neighbor rays but it slightly overgrows the neighboring rays and presents the characteristic white cells of R1. Arrowheads show segmentation process in the bifurcated ray. Scale bars represent 25 (F), 33 (C), 50 (E), 100 (A, G, H), and 200 μm (B, D, I).