Fig. 2

Fig. 2 Bifurcation of the regenerating ray depends on the presence of surrounding interray blastemas. (A) Detail of the central rays (R9) of the dorsal (R9d) and ventral (R9v) lobes of the tail fin of D. rerio at the level of first bifurcations. Note that they are segmented and bifurcated. I9, interray 9. (B) Detail of R1 and R2 distal to the first bifurcation of R2. Note that R1 does not bifurcate and R2 (arrowheads) shows an asymmetrical pattern of bifurcations in which the closest branch to R1 (R2a) does not secondarily bifurcate in contrast to the second branch of R2 (R2b). 2bif indicates the second bifurcation in only one of the branches of R2. (C–F) Examples of regenerates obtained following single ray ablation. (C) After 4 days of regeneration, in 57% of the fins, the distal ray blastema is in contact with the distal epidermis. (D) In these cases, the regenerates later form a normal bifurcation with an internal interray space as in the control (χ², f.d.: 2, α: 0.05). (E) In 43% of the fins, 2 or 3 days after single ray ablation (space shown by the arrow), the epithelial tissue fills the entire space between R2 and R4. In these cases, ray regeneration is delayed. (F). These rays do not bifurcate (asterisk) or they seldom do it distally. b, blastema; e, epidermis. All scale bars represent 100 μm.