Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
The anatomy and development of the claws of Xenopus laevis (Lissamphibia: Anura) reveal alternate pathways of structural evolution in the integument of tetrapods.
Maddin HC
,
Eckhart L
,
Jaeger K
,
Russell AP
,
Ghannadan M
.
???displayArticle.abstract???
Digital end organs composed of hard, modified epidermis, generally referred to as claws, are present in mammals and reptiles as well as in several non-amniote taxa such as clawed salamanders and frogs, including Xenopus laevis. So far, only the claws and nails of mammals have been characterized extensively and the question of whether claws were present in the common ancestor of all extant tetrapods is as yet unresolved. To provide a basis for comparisons between amniote and non-amniote claws, we investigated the development, growth and ultrastructure of the epidermal component of the claws of X. laevis. Histological examination of developing claws of X. laevis shows that claw formation is initiated at the tip of the toe by the appearance of superficial cornified cells that are dark brown. Subsequent accumulation of new, proximally extended claw sheath corneocyte layers increases the length of the claw. Histological studies of adult claws show that proliferation of cornifying claw sheath cells occurs along the entire length of the claw-forming epidermis. Living epidermal cells that are converting into the cornified claw sheath corneocytes undergo a form of programmed cell death that is accompanied by degradation of nuclear DNA. Subsequently, the cytoplasm and the nuclear remnants acquire a brown colour by an as-yet unknown mechanism that is likely homologous to the colouration mechanism that occurs in other hard, cornified structures of amphibians such as nuptial pads and tadpole beaks. Transmission electron microscopy revealed that the cornified claw sheath consists of parallel layers of corneocytes with interdigitations being confined to intra-layer contacts and a cementing substance filling the intercorneocyte spaces. Together with recent reports that showed the main molecular components of amniote claws are absent in Xenopus, our data support the hypothesis that claws of amphibians likely represent clade-specific innovations, non-homologous to amniote claws.
Alibardi,
Hard cornification in reptilian epidermis in comparison to cornification in mammalian epidermis.
2007, Pubmed
Alibardi,
Hard cornification in reptilian epidermis in comparison to cornification in mammalian epidermis.
2007,
Pubmed
Alibardi,
Immuno-cross reactivity of transglutaminase and cornification marker proteins in the epidermis of vertebrates suggests common processes of soft cornification across species.
2004,
Pubmed
Alibardi,
Ultrastructural localization of histidine-labelled interkeratin matrix during keratinization of amphibian epidermis.
2003,
Pubmed
Alibardi,
Keratinization in the epidermis of amphibians and the lungfish: comparison with amniote keratinization.
2001,
Pubmed
Bragulla,
On the development of the papillary body in the feline claw.
2001,
Pubmed
Bryant,
Claw retraction and protraction in the Carnivora: skeletal microvariation in the phalanges of the Felidae.
1996,
Pubmed
Budtz,
Structure of the toad epidermis during the moulting cycle. L. Light microscopic observations in Bufo bufo (L.).
1973,
Pubmed
Budtz,
Structure of the toad epidermis during the moulting cycle. II. Electron microscopic observations on Bufo bufo (L.).
1975,
Pubmed
Cheng Kaung,
Cell turnover in the beak of Rana pipiens.
1977,
Pubmed
de Berker,
Proliferative compartments in the normal nail unit.
1996,
Pubmed
Eckhart,
Identification of reptilian genes encoding hair keratin-like proteins suggests a new scenario for the evolutionary origin of hair.
2008,
Pubmed
Estabel,
Programmed cell death in Xenopus laevis spinal cord, tail and other tissues, prior to, and during, metamorphosis.
2003,
Pubmed
,
Xenbase
Fischer,
DNase1L2 degrades nuclear DNA during corneocyte formation.
2007,
Pubmed
Forbes,
The developmental cytology of the nuptial pad in the red-spotted newt.
1975,
Pubmed
Hamrick,
Development and evolution of the mammalian limb: adaptive diversification of nails, hooves, and claws.
2001,
Pubmed
Hamrick,
Evolution and development of mammalian limb integumentary structures.
2003,
Pubmed
Homberger,
The structure of the cornified claw sheath in the domesticated cat (Felis catus): implications for the claw-shedding mechanism and the evolution of cornified digital end organs.
2009,
Pubmed
Hoperskaya,
The development of animals homozygous for a mutation causing periodic albinism (ap) in Xenopus laevis.
1975,
Pubmed
,
Xenbase
Jäger,
Terminal differentiation of nail matrix keratinocytes involves up-regulation of DNase1L2 but is independent of caspase-14 expression.
2007,
Pubmed
JORGENSEN,
FURTHER OBSERVATIONS ON MOLTING AND ITS HORMONONAL CONTROL IN BUFO BUFO (L.).
1964,
Pubmed
Kato,
A study on the development of the cat claw.
1977,
Pubmed
Kaung,
Development of beaks of Rana pipiens larvae.
1975,
Pubmed
Lavker,
Horny cell formation in the epidermis of Rana pipiens.
1974,
Pubmed
Maddin,
Histological microstructure of the claws of the African clawed frog, Xenopus laevis (Anura: Pipidae): implications for the evolution of claws in tetrapods.
2007,
Pubmed
,
Xenbase
PARAKKAL,
A STUDY OF THE FINE STRUCTURE OF THE EPIDERMIS OF RANA PIPIENS.
1964,
Pubmed
Plikus,
Morpho-regulation of ectodermal organs: integument pathology and phenotypic variations in K14-Noggin engineered mice through modulation of bone morphogenic protein pathway.
2004,
Pubmed
San Mauro,
Initial diversification of living amphibians predated the breakup of Pangaea.
2005,
Pubmed
Vickaryous,
'The integument story: origins, evolution and current knowledge'.
2009,
Pubmed
Witten,
Seasonal changes in the lower jaw skeleton in male Atlantic salmon (Salmo salar L.): remodelling and regression of the kype after spawning.
2003,
Pubmed
Wu,
Molecular evolution of the keratin associated protein gene family in mammals, role in the evolution of mammalian hair.
2008,
Pubmed
