Vladimir Ovchinnikov, Marcela Uliano-Silva, Mark Wilkinson, Jonathan Wood, Michelle Smith, Karen Oliver, Ying Sims, James Torrance, Alexander Suh, Shane A. McCarthy, Richard Durbin, Mary J. O’Connell.
We present genome sequences for Geotrypetes seraphini (3.8Gb) and Microcaecilia unicolor (4.7Gb) caecilians, a limbless, mostly soil-dwelling amphibian clade with reduced eyes, and unique putatively chemosensory tentacles. We identify signatures of positive selection unique to caecilians in 1,150 orthogroups, with enrichment of functions for olfaction and detection of chemical signals. All our caecilian genomes are missing the ZRS enhancer of Sonic Hedgehog, shown by in vivo deletions to be required for limb development in mice and also absent in snakes, thus revealing a shared molecular target implicated in the independent evolution of limblessness in snakes and caecilians.
