Abstract
Fish have a high ability to regenerate fins, including the caudal fin. After caudal fin amputation, original bi-lobed morphology is reconstructed during its rapid regrowth. It is still controversial whether positional memory in the blastema cells regulates reconstruction of fin morphology as in amphibian limb regeneration, in which limb blastema cells located at the same proximal-distal level have the same positional identity. We investigated growth period and growth rate in zebrafish caudal fin regeneration. We found that both the growth period and growth rate differed for fin rays that were amputated at the same proximal-distal level, indicating that it takes different periods of time for fin rays to restore their original lengths after straight amputation. We also show that more proximal amputation takes longer period to reconstruct the original morphology/size than more distal amputation. Statistical analysis suggested that both the growth period/rate are determined by amputated length (depth) regardless of the fin ray identity along dorsal-ventral axis. In addition, we suggest the possibility that the structural/physical condition such as width of the fin ray at the amputation site (niche at the stump) may determine the growth period/rate.
Highlights
Fish have a high ability to regenerate fins, including the caudal fin
To reconstruct the bi-lobed caudal fin morphology during regeneration, each fin ray must regrow to a certain length to restore its original length, depending on the fin ray identity along the dorsal-ventral axis (DR1-8, VR1-8)
In straight-amputation experiments, we found that the longer fin rays in the lobe region had longer growth period and faster growth rate than the shorter fin rays in the cleft region
Summary
Original bi-lobed morphology is reconstructed during its rapid regrowth It is still controversial whether positional memory in the blastema cells regulates reconstruction of fin morphology as in amphibian limb regeneration, in which limb blastema cells located at the same proximal-distal level have the same positional identity. De-differentiation, blastema formation, and tissue re-differentiation have been intensively studied in zebrafish, how the regenerating fin reconstructs its original morphology, that is, regeneration of the original length of the fin rays, remains unclear. It is unknown whether positional memory is involved in zebrafish caudal fin regeneration to reconstruct the original morphology as with the amphibian limb regeneration (Fig. 1a,b). The contribution of positional memory in the blastema to the reconstruction of the whole morphology of the caudal fin is still under debate
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