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Published on: January 12, 2015
Limb development in a "nonmodel" vertebrate, the direct-developing frog Eleutherodactylus coqui.
J Hanken1, T F Carl, M K Richardson
1Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA. hanken@oeb.harvard.edu
The Journal of Experimental Zoology
|December 26, 2001
Summary
Limb development in the direct-developing frog Eleutherodactylus coqui shows conserved and novel features, challenging assumptions about conserved tetrapod limb development. This variation highlights evolutionary plasticity in developmental processes.
Area of Science:
- Developmental Biology
- Evolutionary Biology
- Amphibian Biology
Background:
- Vertebrate limb development is assumed to be highly conserved, particularly in tetrapods.
- This assumption is based on limited species, neglecting diverse life histories like direct development in anurans.
- Direct-developing anurans exhibit adult features, such as limbs, during embryogenesis, unlike metamorphic frogs.
Purpose of the Study:
- To investigate limb development in the direct-developing frog Eleutherodactylus coqui.
- To identify conserved and novel mechanisms in Eleutherodactylus coqui limb development.
- To assess the impact of direct development on conserved tetrapod limb developmental patterns.
Main Methods:
- Comparative analysis of limb chondrogenesis patterns.
- Examination of Distal-less protein (Dlx) and Sonic hedgehog (Shh) gene expression.
- Chirality analysis of limb development.
- Transplantation experiments involving the zone of polarizing activity (ZPA).
Main Results:
- Limb development in Eleutherodactylus coqui displays conserved features like chondrogenesis patterns, Dlx expression, and Shh signaling in the ZPA.
- Novel features include the absence of a distinct apical ectodermal ridge and continued outgrowth after distal ectoderm removal.
- The ZPA shows earlier cessation of inductive ability compared to metamorphic frogs.
Conclusions:
- Limb development in Eleutherodactylus coqui is a mosaic of conserved and novel mechanisms.
- Direct development significantly influences limb developmental timing and processes.
- Tetrapod limb development exhibits greater evolutionary variation than previously assumed, requiring flexible models.
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