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. 2014 Nov 25;14:230. doi: 10.1186/s12862-014-0230-z

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© Voigt et al.; licensee BioMed Central Ltd. 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Spicules and their formation in S. ciliatum . (a) Formation of diactines and triactines by sclerocytes in calcareous sponges (redrawn from [18,19]). (b) isolated spicules; scale bar: 100 μm. (c) skeletal arrangement; scale bar: 250 μm. (d) Spicule growth in 18 h observed in three spicule types of S. ciliatum. (e-g) Location of spicule formation in S. ciliatum (calcein disodium staining). Single spicules are formed all over the sponge body, with two regions of denser spicule formation: (1) the radial tube formation zone (white arrow, e) and the proximal tips of the slender diactines of the osculum (inside the osculum, grey arrow: f, g); scale bars: 250 μm. b,c,e: light microscopic images overlayed with fluorescence microscope images. f,g: fluorescence microscope images. Abbreviations: di(c) curved diactines from the distal end of the radial tubes; di(s): slender diactines of the oscular fringe; f: founder cell; t: thickener cell; tri: triactines; tet: tetractines.