Regeneration in Reptiles Generally and the New Zealand Tuatara in Particular as a Model to Analyse Organ Regrowth in Amniotes: A Review

J. Dev. Biol., 2021 · DOI: https://doi.org/10.3390/jdb9030036 · Published: August 30, 2021

Genetics Regenerative Medicine & Stem Cells

Simple Explanation

Reptiles can repair injuries, similarly to mammals, though with exceptions. Turtles and crocodilians heal large wounds with scars. Tail repair involves wound healing and somatic growth. Injured tails in young crocodilians, turtles, tortoises, and tuatara undergo “regengrow,” where the wound heals and cartilage regenerates during growth. The regrown tail of the tuatara, unlike the original, consists mostly of irregular connective tissue with fat cells and sparse nerves around a cartilaginous axis.

Study Duration

Not specified

Participants

Three young tuatara, histological samples from older specimens

Evidence Level

Review

Key Findings

1
Tuatara tail regeneration is a slow process that combines regeneration and growth (“regengrow”), resulting in tails with a cartilaginous axis, connective tissue, fat cells, and sparse nerves.
2
Cell proliferation is active in the apical regenerative blastema, but much reduced cell proliferation continues in older regenerated tails, where it occurs mostly in the axial cartilage and scale epidermis of the new tail.
3
Repeated tail regeneration in tuatara influences normal growth, potentially causing a loss of body length compared to expected growth rates.

Research Summary

Reptiles, similar to mammals, exhibit injury repair capabilities, but differ in their ability to regenerate lost structures. While scarring is the primary repair mechanism for large wounds in turtles and crocodilians, tail regeneration in these reptiles and the tuatara involves a combination of wound healing and somatic growth, termed “regengrow”. The tuatara's tail regeneration is a protracted process. This results in a tail composed of a cartilaginous axis, connective tissue, fat cells, and sparse nerves, which impacts the overall growth of the animal. Cell proliferation studies in regenerated tuatara tails reveal active growth in the cartilage and scales, suggesting a continued, albeit slow, process of tissue development and remodeling.

Practical Implications

Understanding Amniote Regeneration

Studying regeneration in reptiles, especially the tuatara, can provide insights into the limited regenerative capacity of amniotes, including humans.

Improving Healing Processes

Information gained from reptile regeneration can inform strategies to enhance healing and minimize scarring in amniotes.

Evolutionary Scenarios

Regenerative studies contribute to understanding the evolutionary pathways and specializations of reptiles and their scales.

Study Limitations

1
Limited data on the precise duration of tail regeneration in chelonians.
2
Lack of comprehensive microscopic descriptions of wound healing in Sphenodon.
3
The precise three-dimensional shape of segmental muscles in the regenerated tail remains undetermined.

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