Sponges are sessile filter feeding animas, but nevertheless they exhibit behaviours which base on movement and hence temporarary structural modifications of their tissue and skeletons. In most cases, these movements are so slow that they are not easily recognized by an observer without technical support. In some species, these movements are much faster and can be recognized and recorded more easily. Especially specimens of the genus Tethya display movements in form of body dislocation, contraction and formation of body extensions.
These movements are far from beeing random. They are controlled by the sponge and therefore sponges must have the capability of integrating internal and external signals. On the other hand, a nervous system or nerv cells have never been found in sponges. Since sponges are ancient organisms under an evolutionary point of view, they are interesting model organisms to unreavel questions upon the development of early metazoan signalling mechanisms. Questions raise for the signalling components: What kind of receptors are involved? Which signalling molecules? Is ther a signalling network and how does this system work? This leads us to systems biology. And what about other ways of signalling, eg. mechanical signals? Hence there are also morphological questions link to this movement behaviours: how does it work? Most demosponges possess skeletons made from silica spicules. What are the static principles behind skeletal and tissue dynamics? We can go even further: can we find technical principles which are yet unknown? This leads us to material sciences and construction.
Our "lab-rat" for most of our investigations is Tethya wilhelma, a previously unknown species, we found in 1999 the aquarium of the zoological-botanical garden "Wilhelma" (Wilhelma). The advantage of this species is that it is small and reproduces asexually by budding, so we can easily maintain, cultivate and breed it in a tropical aquarium of around 100 l size.
Currently we focus on the following topics:
- Structural characterization of the functional morphology (statics and dynamics)
- Characterization of contractions and underlying rhythms
- Physiological characterization of signal substances, receptors and inhibitors
- Molecular characterization of receptors