Cnidaria is an ancient phylum that includes solitary organisms like Hydra and sea anemones and colonial organisms like corals. Because of their apparent lack of bilaterality and their simple body plan, Cnidarians were considered very unsophisticated organisms that should be easy to understand. This view, however, has changed recently due to the discovery of numerous Cnidarian genes and signaling molecules that are also present in "higher" organisms.

For a long time Hydra has been a model system for developmental biology and a favorite pet for theorists. It is remarkable for its extraordinary regeneration capabilities that enable the survival of the organism from only 1% of the body tissue. In the course of regeneration Hydra forms a hollow sphere that undergoes cycles of oscillations. The purpose of the oscillations has not yet been completely understood but is likely due to osmoregulation, as I will argue in my talk.

Corals give rise to one of the world's most diverse ecosystems and fascinate because of their bright colors and fantastic shapes. How these different shapes are created is still very much unclear. On the one hand, genetic dispositions must be important; on the other hand, environmental factors such as light and water flow modulate the growth significantly. In my talk I will summarize experimental work geared towards deciphering the rules of growth in the coral Stylophora pistillata and present a model setup for studying these rules.