Figure 2
Magnetic resonance imaging: potential and limitations for comparative morphological analyses. Vertical MRI sections of two sea urchin (Echinoidea) species passing from pharynx to periproct. A Psammechinus miliaris (Müller, 1771), (44 μm)3 dataset resolution, contrast agent: Magnevist. B Inset from A showing the stomach (st) with adjacent siphon (si) and inner marginal sinus (ims). C Diadema savignyi Michelin, 1845, (40 μm)3 dataset resolution, contrast agent: Magnevist. D Inset from C showing the stomach (st) with siphonal groove (sg) and adjacent inner marginal sinus (ims). Although both scans permit to differentiate various minute and large structures, the inner marginal sinus (ims) present in D. savignyi can be mistaken for a siphon. Vertical sections and magnifications were generated using the Volume Viewer in ImageJ 1.41o.