NICKEL, M.*; BECKMANN, F.; Biological Institute of University Stuttgart, Germany; HASYLAB at DESY, Hamburg, Germany: Sponge skeletons in 3D: Synchrotron x-ray computed microtomography (�CT) as a tool for functional morphology and taxonomy

Sponges (Porifera) possess a mineral skeleton made of siliceous or calcareous spicules. The types of spicules as well as their orientation inside the sponge tissue are attributes for the taxonomic classification and reflect the sponge’s functional morphology. Up to now it was not possible to obtain direct data on the 3D-structure by light or electron microscopy, due to methodological limitations by preparation or microscopy techniques. Using �CT we were able to reconstruct the 3D image of a complete skeleton of Tethya minuta (Demospongiae, Hadromerida; � ~ 5 mm) at a resolution of 4.2 �m. We used the BW2-beamline of the HASYLAB at DESY equipped with a x-ray microtomography camera at the photon-energy of 9 keV to obtain intensity profiles with and without the sample at different sample rotation. A z-stack of 401 images of 3.5 �m distance was calculated from 720 radiograms equally stepped between 0 and π using the tomographic-reconstruction algorithm of back projection of filtered projections. 3-dimensional visualisation by the software VGStudio revealed the complete skeleton arrangement of the megascleres (anisostrongyles and spherasters). The microscleres (tylasters, � > 10 �m) cannot be resolved as single particles, but areas of higher tylaster-density can be visualised. The arrangement of anisostrongyles is important for the fast formation of body extensions and the locomotion of the body of T. wilhelma. �CT will give new insights in functional morphology of sponge skeletons and can also be used as a tool for the taxonomy of difficult sponge groups.