Note on the partial regeneration of the caudal region of Sphenodon punctatum

Byerly, T. C.

doi:10.1002/ar.1090300105

Cited by 15 publications

(14 citation statements)

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“…Furthermore, as the blastema grows into a cone the mesenchyme is rapidly turned into a dense and irregular connective tissue to which numerous collagen bundles secreted by residing fibroblasts contribute; a process that results in the rapid formation of scarring tissue. The dermis of the regenerated tail does not turn into a deep, dense layer like in the normal tail (Byerly, ), but instead appears as a uniformly dense connective tissue extending from the epidermis to the regenerated muscles. The richness of this fibrotic tissue was also noted in regenerated tails found in the wild (Byerly, ; Woodland, ).…”

Section: Discussionmentioning

confidence: 99%

“…The dermis of the regenerated tail does not turn into a deep, dense layer like in the normal tail (Byerly, ), but instead appears as a uniformly dense connective tissue extending from the epidermis to the regenerated muscles. The richness of this fibrotic tissue was also noted in regenerated tails found in the wild (Byerly, ; Woodland, ). The dense connective tissue present in the new tail may largely derive its consistency from the dense dermal layer and the intermuscle connective of the normal tail (Byerly, ).…”

Section: Discussionmentioning

confidence: 99%

“…In lizards, the regenerated fat occupies large regions of the pericartilaginous connective tissue, where it is important as an energy storage. However, fat tissue and large segmented muscles may increase in older regenerates (Byerly, ).…”

Section: Discussionmentioning

confidence: 99%

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Microscopical observations on the regenerating tail in the tuataraSphenodon punctatusindicate a tendency to scarring, but also influence from somatic growth

Alibardi

Meyer‐Rochow

2019

Journal of Morphology

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The process of tail regeneration in the tuatara (Sphenodon punctatus) is not entirely known. Similarity to and differences from lizard tail regenerations are indicated in the present histological and ultrastructural study. Regeneration is influenced by the animal's age and ambient temperature, but in comparison to that of lizards it is very slow and tends to produce outgrowths that do not reach the length of the original tail. Although microscopically similar to lizard blastemas, the mesenchyme rapidly gives rise to a dense connective tissue that contains few muscle bundles, nerves, and fat cells. The unsegmented cartilaginous tube forming the axial skeleton is not calcified after 5 months of regeneration, but calcification in the inner region of the cartilage, present after 10 months, increases thereafter. Amyelinic and myelinic peripheral nerves are seen within the regenerating tails of 2–3 mm in length and the spinal cord forms an ependymal tube inside a cartilaginous casing. Tissues of the original tail, like muscles, vertebrae and the adipose mass, are largely replaced by dense connective tissue that occupies most of the volume of the new tail at 5 and 10 months of regeneration. It is unknown whether the differentiation of the dense connective tissue is caused by the relatively low temperature that this species lives under or stems from a genetic predisposition toward scarring as with most other amniotes. Increases of muscle and adipose tissues seen in older regenerated tails derive from somatic growth of the new tail in the years following tail loss and not from a rapid regeneration process like that in lizards.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Microscopical observations on the regenerating tail in the tuataraSphenodon punctatusindicate a tendency to scarring, but also influence from somatic growth

Alibardi

Meyer‐Rochow

2019

Journal of Morphology

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“…The regenerated axial skeleton was briefly described by Byerly (1925) as a tube of hyaline cartilage with calcifications dorsally and laterally. Ali (1941) described it as a cartilage tube that, as in Hemidactylus (Woodland, 1920), is calcified on the tube's outer and inner surfaces.…”

Section: Morphological Aspectsmentioning

confidence: 99%

Morphological, functional and evolutionary aspects of tail autotomy and regeneration in the ‘living fossil’Sphenodon (Reptilia: Rhynchocephalia)

Seligmann

Moravec

Werner

2008

Biological Journal of the Linnean Society

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Tail autotomy and regeneration are less known in Sphenodon ('Reptilia': Rhynchocephalia) than in Squamata. We examined museum specimens, Sphenodon guntheri (N = 8) and Sphenodon punctatus (N = 172), wild Sphenodon punctatus (N = 19) and Sphenodon sp. skeletons (N = 8). In S. punctatus, unlike in typical Squamata, sexes had similar relative (intact) tail lengths, and regeneration frequencies; tail and body growth was isometric. Tail breakage was usually intravertebral, usually followed by ablation of a variably sized terminal vertebral piece, partly deviating from lizards. Hypothetically, imperfect autotomy results from sphenodon's primitiveness. As in squamates, tail-losers were morphologically more left-side dominant than tail-retainers. Individual directional asymmetries in digit morphology and in digit injury were correlated (in lizards observed only at population level); tail-losers had more fluctuating asymmetry but their exclusion did not facilitate morphological taxonomic distinctions (no 'Seligmann effect'). In S. punctatus, extents and directions of sexual dimorphism paralleled differences between tail-retainers and tail-losers, females resembling tail-losers, also accounting for character interdependence (developmental constraints; employing a method similar to phylogenetic contrasts). The variation in the location of tail injury was correlated with the continuum of variation between injured and intact (pholidotic) morphotypes. These last two phenomena remain to be explored in Squamates.

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“…Little is known about caudal skin replacement in S. punctatus beyond the fact that regenerated tails are covered with scales that are small and irregularly placed, by comparison with those covering the intact organ (Woodland, 1920;Byerly, 1925;Alibardi and Meyer-Rochow, 1989;Alibardi, 1990Alibardi, -1991.…”

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confidence: 99%

Observations on the histochemistry and ultrastructure of regenerating caudal epidermis of the tuatara Sphenodon punctatus (Sphenodontida, Lepidosauria, Reptilia)

Alibardi

Maderson

2003

Journal of Morphology

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Study of the histology, histochemistry, and fine structure of caudal epidermal regeneration in Sphenodon punctatus through restoration of a scaled form reveals that the processes involved resemble those known in lizards. Following establishment of a wound epithelium (WE), subjacent scale neogenesis involves epidermal downgrowths into the dermis. Although the process is extremely slow, and most new scales do not overlap, their epidermal coverings reestablish epidermal generation (EG) formation. As in lizards, the flat, alpha-keratogenic, WE cells contain lipids as revealed by their affinity for Sudan III. A few mucous cells that store large PAS-positive mucus-like granules also occur in WE. During differentiation of WE cells, among the bundles of 70-nm tonofilaments are many lamellar bodies (LBs) and mucous granules (MGs) that discharge their contents into the cytoplasm and extracellular spaces producing a strongly PAS-positive keratinized tissue. Richness of epidermal lipids coexistent with mucus is a primitive characteristic for amniote vertebrates, probably related to functions as a barrier to cutaneous water loss (CWL). As scale neogenesis begins, beneath the superficial WE appear 3-5 layers of irregularly shaped cells. These contain tonofilament bundles surrounded by small, round keratohyalin-like granules (KHLGs) and a keratinized matrix with beta-keratin packets and a 3-5-nm thick keratin granulation. This mixture of alpha- and beta-keratogenic capacities resembles that seen in the innermost cells of a normal tuatara epidermal generation. As in the latter, but in contrast to both normal and regenerating lizard epidermis, no definable shedding complex with interdigitating clear layer and oberhautchen cells occurs (Alibardi and Maderson, 2003). The tortuous boundaries, and merging beta-keratin packets, identify subjacent keratinizing cells as precursors of the typical stratified, squamous beta-layer seen in long-term regenerated caudal skin wherein the entire vertical sequence of epidermal layers resembles that of normal scales. The sequence of events in caudal epidermal regeneration in S. punctatus resembles that documented for lizards. Observed differences between posttrauma scale neogenesis and scale embryogenesis are responses to functional problems involved in, respectively, restoring, or forming, a barrier to CWL while accommodating rapid somatic growth.

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Note on the partial regeneration of the caudal region of Sphenodon punctatum

Cited by 15 publications

References 0 publications

Microscopical observations on the regenerating tail in the tuataraSphenodon punctatusindicate a tendency to scarring, but also influence from somatic growth

Microscopical observations on the regenerating tail in the tuataraSphenodon punctatusindicate a tendency to scarring, but also influence from somatic growth

Morphological, functional and evolutionary aspects of tail autotomy and regeneration in the ‘living fossil’Sphenodon (Reptilia: Rhynchocephalia)

Observations on the histochemistry and ultrastructure of regenerating caudal epidermis of the tuatara Sphenodon punctatus (Sphenodontida, Lepidosauria, Reptilia)

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