a geobiological portrait

researc

Coralline demosponges ; a geobiological portrait

The polyphyletic coralline demosponges possess a calcareous basal skeleton of 4 major morphotypes. Each has its own phylogenetic history, with different mechanisms of formation. One extant taxon of each skeletal type has been investigated, and its biochemical (e.g., intracrystalline organic matrix proteins), geochemical (e.g., stable isotopes), and histological properties described in detail. The thalamid Vaceletia shows similarities in its skeletal features to extinct archaeocyathid sponges due to the presence of special Ca2+ waste deposit chambers in the lower part of the skeleton. In our opinion this type is phylogenetically the most important one because it represents one possible evolutionary way of Ca2+ detoxification and iIIustrates one function of basic biomineralization (Ca2+-detoxification). More sophisticated biomineralization processes are developed in the agelasid Ceratoporella, the "chaetetid" hadromerid sponge Spirastrella (Acanthochaetetes) weil si, and the "stromatoporoid" agelasid Astrosclera willeyana. Each of these taxa shows a distinct process of formation with a unique composition of its intracrystalline organic matrix and geochemical features, here characterized in detail. A model of phylogenetic relationships and grades of development is proposed. The first metazoans with CaC03 biomineralization were the worm- like Cloudinidae from the late Sinian, which form a tube with a foliated structure. However, the taphonomy- controlled mode of basal skeleton formation in Archaeocyatha and Vaceletidae is the most ancient type of biologically- controlled metazoan biomineralization. In general, basal skeletons of coralline sponges represent the simplest biologically controlled mineralization, intermediate between biologically induced type (e.g., organomineralization) and the fully enzymatically- controlled mineralization of higher Metazoa

Widefield deconvolution epifluorescence microscopy combined with fluorescence in situ hybridization reveals the spatial arrangement of bacteria in sponge tissue

Widefield deconvolution epifluorescence microscopy (WDEM) combined with fluorescence in situ hybridization (FISH) was performed to identify and characterize single bacterial cells within sections of the mediterranean sponge Chondrosia reniformis. Sponges were embedded in paraffin wax or plastic prior to the preparation of thin sections, in situ hybridization and microscopy. Serial digital images generated by widefield epifluorescence microscopy were visualized using an exhaustive photon reassignment deconvolution algorithm and three-dimensional rendering software. Computer processing of series of images taken at different focal planes with the deconvolution technique provided deblurred three-dimensional images with high optical resolution on a submicron scale. Results from the deconvolution enhanced widefield microscopy were compared with conventional epifluorescent microscopical images. By the application of the deconvolution algorithm on digital image data obtained with widefield epifluorescence microscopy after FISH, the occurrence and spatial arrangement of Desulfovibrionaceae closely associated with micropores of Chondrosia reniformis could be visualized