Figure 2.

CµXRF analysis results of selected I. basta skeletal samples after treatment with distilled water (a), 3 M HCl (b), and 10% NaOH at 40 °C (c). The 3D distribution of Ca (red) and Br (green) is illustrated in the figure for an analyzed sample volume of 1.5 × 1.5 × 1.5 mm³ (and locations with both elements are shown in a yellow coloration). By HCl treatment the Ca is removed from the skeletal structure (b), whereas by NaOH treatment both elements, Ca and Br, remain within the demosponge, however thin proteinaceous tissue layers between the sponge’s skeleton are dissolved (c) and characteristic 3D chitinous construct remains present [17]. In figures (d,e) the sponge structure of (a,b) is depicted without the above-mentioned thin tissue layers, which was obtained by omitting the regions with very low signal intensity from data processing.