Dynamics of skeleton formation in the Lake Baikal sponge Lubomirskia baicalensis. Part I. Biological and biochemical studies |
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Authors: | Oxana V Kaluzhnaya Sergey I Belikov Heinz C Schröder Matthias Rothenberger Stefan Zapf Jaap A Kaandorp Alexandra Borejko Isabel M Müller Werner E G Müller |
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Institution: | (1) Limnological Institute of the Siberian Branch of Russian Academy of Sciences, Ulan-Batorskaya 3, 664033 Irkutsk, Russia;(2) Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität Mainz, Duesbergweg 6, 55099 Mainz, Germany;(3) Klinik und Poliklinik für Radiologie, Universitätsklinikum, Langenbeckstrasse 1, 55131 Mainz, Germany;(4) Faculty of Mathematics, Computer Science, Physics &; Astronomy, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands; |
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Abstract: | In ancient Lake Baikal (East Siberia), freshwater sponges have diversified to an extraordinary degree. The skeleton of Lubomirskia baicalensis, which attains a size of up to 1 m, is constructed from spicules, which are cemented into longitudinal bundles. Our X-ray analysis revealed that the architecture of the specimens follows a highly ordered radiate accretive growth pattern. The spicules have a central axial canal with an axial filament inside. This organic filament is composed of silicatein, the major enzyme involved in silica formation of the spicules. We found that the specific activity of silicatein in samples from the non-growing (basal) zone is much lower than in those from the growth zone (tips) and that even the composition of this molecule differs in these regions. The present study shows for the first time that the turnover of silicatein, the major element of the axial canal of sponge spicules, changes within a sponge specimen depending on the region in which it is found. |
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