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Developmental basis of evolutionary lung loss in plethodontid salamanders
Zachary R Lewis1, Ryan Kerney2, James Hanken1
1Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA.
Science Advances
|August 17, 2022
Summary
Lung development in lungless salamanders (Plethodontidae) involves transient embryonic lung primordia that regress. This developmental pathway offers insights into amphibian lung loss and conserved genetic mechanisms.
Area of Science:
- Developmental Biology
- Evolutionary Biology
- Amphibian Anatomy
Background:
- Four amphibian clades independently lost pulmonary respiration, yet the developmental basis of lung loss remains largely unknown.
- The Plethodontidae family of salamanders represents a dominant group entirely lacking lungs in adulthood.
Purpose of the Study:
- To investigate the developmental basis of lung loss in the Plethodontidae salamander family.
- To determine if lung developmental pathways are conserved in lungless amphibians.
Main Methods:
- Morphological analysis
- Molecular techniques
- Experimental approaches
- Gene expression analysis (Wnt2b, Nkx2.1, Sox9)
Main Results:
- Plethodontids form transient embryonic lung primordia that undergo apoptosis before hatching.
- Lung development initiation correlates with Wnt2b gene expression.
- Pulmonary marker genes Nkx2.1 and Sox9 are expressed in lung rudiments.
- Altered signaling molecule expression is associated with adult lung loss.
Conclusions:
- Lung developmental-genetic pathways are partially conserved in lungless salamanders despite millions of years of lung absence.
- Embryonic lung development and subsequent regression is a key feature of lung loss in Plethodontidae.
