Project title: Evolution of axis specification in annelid worms
Summary: Spiralian organisms (e.g. annelids, molluscs and flatworms) display a highly conserved cleavage pattern in early development, contrasting with their vast morphological diversity as adults. Despite the conservation in early development, spiralian animals exhibit two major modes of early cell fate specification, namely the equal (or conditional) and unequal (or autonomous) mode. The equal cleavage pattern is often considered as the ancestral spiralian condition, yet how this pattern evolved and which mechanisms control it remain unclear. My phD project addresses these questions by exploring the early development of the equal cleaving polychaetes Owenia fusiformis, the sister lineage to all remaining annelids, and Spirobranchus triqueter. This will allow me to dissect the molecular and genetic pathways underlying equal cleavage, characterise its cellular dynamics, and use a comparative approach to uncover the evolution of cleavage patterns and axis specification in spiralians.