The genetic basis of a morphological key trait: radula genes and the adaptive radiation of the freshwater snail Tylomelania

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Specializations of the feeding organs play a crucial role in many adaptive radiations. This is also true for the freshwater gastropod Tylomelania, which has evolved an unparalled diversity of radula (rasping tongue) forms in the course of its radiation in ancient lakes on the Indonesian island Sulawesi. The genetic basis of this key phenotypic trait is entirely unknown. The aim of this project is the identification of candidate genes for radula formation and shape by focussing on one species, T. sarasinorum, with two highly distinct radula morphs. Transcriptomes of several individuals from both morphs and three tissues each will be sequenced with a high coverage using Next Generation Sequencing (Illumina). The primary analysis of gene expression differences between tissues and morphs will be complemented by looking at gene function and SNP differences. The actual involvement of the putative candidate genes for radula formation identified from the transcriptome data will be tested by in situ hybridization experiments, whose interpretation will be aided by data on the ultra-anatomy of the radula forming tissue. The identification of genes involved in creating the radula differences observed Tylomelania will be a crucial step towards understanding key processes of this adaptive radiation at the genetic level.