Figure 1
From: Proteomic analysis of sea urchin (Strongylocentrotus purpuratus) spicule matrix
Purified S. purpuratus spicules visualized by scanning electron microscopy. A, section showing fragments of spicules prepared from pluteus larvae. Fragmentation is due to fractures caused by homogenization during purification. Maximal length of spicule fragments is 70-80 μm. B, higher magnification showing the clean surfaces of spicule fragments. C, cross-section of a fractured spicule with a diameter of 4 μm showing the concentric layers of mineral. D, deeper etching and higher magnification reveals presumed matrix fibers coursing through the mineral layers.