Mineralization events during growth of the coralline sponges Acanthochaetetes and Vaceletia

Mineralization events are studied in two recent calcified Demospongiae, Acanthochaetetes and Vaceletia, using in vivo stainings by fluorescent Ca-chelating complexes calceins and tetracyclines), SEM examinations of fixed specimens, and biochemical analyses of intraskeletal organic matrices. Actively mineralizing zones are localized in the uppermost parts of skeletal buildings, and also in enclosed cavities within the deep older parts. These zones are characterized by a strong fluorescent behaviour rising from stained specimens, and important amounts of soluble acidic (asparticand glutamic-rich) glycoproteins. Deep skeleton parts are enriched with glucidic compounds when mineralization occurs.