MSc Student
Supervisor: Andreas Wanninger

Unit for Integrative Zoology, Department of Evolutionary Biology
University of Vienna

Abstract

Annelids and arthropods had been considered close relatives for many decades, largely based on their segmented body plans. However, molecular phylogenetic analyses now support a monophyletic assemblage of annelids, molluscs and other spiralian phyla in the so-called Lophotrochozoa, excluding the arthropods.  This hypothesis implies that annelids and molluscs share a closer evolutionary relationship than the annelids do with the arthropods. Thus segmentation might have evolved independently in annelids and arthropods. Regardless of whether segmentation arose through convergent evolution, the varying mechanisms establishing segmentation in early ontogenesis underlie the activity of so-called “segmentation genes”. These include genes like  hairy, engrailed or hedgehog, which were first described in the arthropod Drosophila melanogaster but representative homologs are also present in annelids and chordates.

The aim of this Master Thesis is to gain insight into expression patterns of such “segmentation genes” across diverse development stages of a non-segmented but vermiform mollusk. This descriptive work will create the framework of future studies about the possible additional functions of these genes in non-segmented animals. To achieve this, whole-mount in situ hybridization experiments will be conducted on the non-model organism Thylaedus rugulosus. This gastropod species belongs to the marine family of Vermetidae (worm snails) and is characterized by striking changes in morphology and lifestyle during ontogeny.