Caecilians (Gymnophiona) are a highly specialized order of extant amphibians with elongate, annulated, limbless bodies, and sensory tentacles on each side of the snout. Most of the 200 currently recognized species have a secretive fossorial lifestyle, and members of one family are secondarily adapted to aquatic habitats. Of the many evolutionary and ecological features that make caecilians so distinct, their great diversity of life history is among the most outstanding.

They have a broad variety of reproductive strategies and types of parental care, matching frogs and salamanders in the main reproductive modes despite there being many fewer caecilian species than there are currently recognized species of salamanders (675) and frogs (6509). Caecilian reproductive strategies encompass oviparity with presence of free-living larva, oviparity with direct development, and viviparity, these combined with varying forms of parental care, including egg attendance and the recently discovered maternal dermatophagy in which hatchlings eat their mothers skin.

Several studies have addressed life-history evolution and/or aspects of reproductive biology of caecilians but, thus far, no modern study has considered a broad sweep of the evolution of reproductive strategies within a phylogenetic framework. We have analyzed mitochondrial genomes to reconstruct an exceptionally robust and comprehensive phylogenetic framework for caecilian amphibians, and have used this to investigate life-history evolution within the group.

Our results have provided evidence that an ancestor of the Seychelles caecilians abandoned direct development and re-evolved a free-living larval stage. Furthermore, our study yielded insights into the concurrent evolution of direct development and of vernal teeth in an ancestor of Teresomata that likely gave rise to skin feeding (maternal dermatophagy) behavior and subsequently enabled the evolution of viviparity, with skin feeding possibly a homologous precursor of oviduct feeding in viviparous caecilians.

Seminario organizado por el Departamento de Biodiversidad y Biología Evolutiva del Museo Nacional de Ciencias Naturales (MNCN), CSIC, y retransmitido en directo a través de Cienciatk.