Meeting Abstract

94.3  Sunday, Jan. 6  Genetic and morphological vestiges of lost lungs in plethodontid salamanders LEWIS, Z*; KERNEY, R; DORANTES, J; HANKEN, J; Harvard Univ., Cambridge, MA; Gettysburg College, Gettysburg, PA; Harvard Univ., Cambridge, MA; Harvard Univ., Cambridge, MA zlewis@oeb.harvard.edu

Vestigial structures and rudiments provide windows into the evolutionary history of animals. Common examples are the transient limb buds or atavistic pelvic girdles found in tetrapods that have undergone limb loss. Vestiges of internal organs have received far less attention, and they have the potential to reveal how organ loss can occur in highly pleiotropic genetic networks and within tightly integrated organ systems. One example of organ loss is the loss of lungs in plethodontid salamanders (Caudata: Plethodontidae). We have discovered several atavistic features of lungless salamanders during both organogenesis and adulthood. Plethodontid embryos form a transient lung rudiment and express lung-specific and functionally significant genes, including surfactant protein C. Surprisingly, adult plethodontids display novel pharyngeal expression of lung-specific transcripts in the absence of lungs. From one perspective, presence of the transient rudiment in embryos suggests conservation of inductive interactions that govern lung formation. In contrast, unanticipated expression patterns of lung-specific transcripts in lungless adults may be an example of evolutionary novelty. In light of our results, we reexamine the idea, proposed first in 1900, that the pharynx may play a significant respiratory role in lungless salamanders. By studying atavistic features of internal organs we have uncovered unexpected conservation of lung developmental-genetic programs following lung loss, as well as a novel expression pattern of a gene that may play important functional roles.