The genetic basis of eye loss in an obligate cave-dwelling planarian of the Bodoquena Plateau in central Brazil (Mato Grosso do Sul)

Abstract

Adaptations to dark environments lead to a convergent loss of eyes in different phyla, resulted by changes in classic eye development genes expression. Planarians are an interesting group to study eye development because adult animals can regenerate their eyes within a week after decapitation, recruiting classic eye development genes orthologues. During my PhD project I found that the obligate cave-dwelling planarian Girardia multidiverticulata, initially described as eyeless, presents two morphotypes among siblings: one completely without eyes, and another with a small rudimentary eye. This finding represents a unique opportunity to study the genetics and plasticity of eye developmental disruption in planarians. Therefore, this project aim to reveal the main molecular players involved in eye loss, as well as to mechanistically reconstruct the evolutionary loss of eyes in planarians. To understand the altered genetic pathways that result in eye developmental diruption, I will identify the differences in eye gene expression during regeneration of the two cave planarian morphotypes, and compare the differentially expressed genes to the gene expression profiles of eye development of the surface specie S. mediterranea. Once particular gene pathways involved in eye loss are identified, I plan to validate these pathways by performing functional knockdown experiments using RNAi to disrupt eye development in S. mediterranea. The results will uncover genes that control or regulate the development of specific structures of the planarian visual system, and increase the understanding over the developmental robustness during the evolution of cave specific adaptations.