Meeting Abstract

14.4  Wednesday, Jan. 4  Pulmonary Surfactant Proteins are Expressed in Lungless Salamanders LEWIS, Zachary*; KERNEY, Ryan; DORANTES, Jorge; HANKEN, James; Museum of Comparative Zoology and Dept. of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States; Biology Department, Dalhousie University, Halifax, NS, Canada; Museum of Comparative Zoology and Dept. of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States; Museum of Comparative Zoology and Dept. of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States zlewis@oeb.harvard.edu

Although lungs have been crucial to the remarkable adaptive radiation of tetrapods, they evolved well before tetrapods emerged onto land. Over the course of evolution, certain amphibians have dispensed with pulmonary respiration altogether, relying instead on cutaneous gas exchange through the skin and the lining of the mouth. Although lung loss was long thought to be restricted to salamanders, recent work has demonstrated lung loss in all three modern orders of amphibians--Anura, Caudata, and Gymnophiona. Yet, it remains unclear why or how lung loss occurs. We have discovered that lungless salamanders (family Plethodontidae) complete early stages of lung morphogenesis and begin to develop lung primordia. Lung rudiments are only transiently present and soon regress, resulting in lung loss. The morphological lung rudiment likely represents retention of the ancestral lunged state. In addition to recapitulation of lung morphogenesis in plethodontid salamanders there is conservation of lung developmental genetic pathways. We report the expression of lung-specific surfactant protein C (SP-C) in plethodontids and examine the expression patterns of surfactant proteins B, C, and D. Expression of surfactant proteins offers compelling evidence that lung developmental genetic pathways are conserved in lungless salamanders, despite absence of functional adult lungs for over 100 million years.

This work was supported by a grant from the William F. Milton Fund, Harvard University (JH), by an NSF Graduate Research Fellowship (ZL), and by the American Association of Anatomists (RK).