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Fig. 2 | EvoDevo

Fig. 2

From: Developing an ancient epithelial appendage: FGF signalling regulates early tail denticle formation in sharks

Fig. 2

Sequential development of caudal denticles in the Catshark. As the embryo develops from Stage 27 (a) to Stage 33 (i), the gills proliferate, the eyes are encircled with pigment of increasing darkness and the rostrum protrudes anterior to the mouth [23]. During this period, caudal denticles develop from posterior to anterior in dorsal and ventral rows, on either side of the tail tip. At early Stage 27, no placodes can be detected (a2a2). Epithelial thickenings then form from posterior to anterior (b2b3, c2c4). c4 shows a magnified view of c3, highlighting an individual placode (marked with an arrowhead). These placodes then accumulate their first layers of mineralised tissue during morphogenesis (d2d4). d4 shows a magnified view of d3, highlighting a mineralising placode (marked with an arrowhead). Mineralisation of denticles also occurs sequentially from posterior to anterior (e2e3, f2f3, g2g3, h2h3 and i2i3) and can be highlighted with alizarin red staining for calcium-rich tissue (e4e5, f4f5, g4g5, h4h5 and i4i5). For the axis, D dorsal, V ventral, P posterior and A anterior. Scale bars are 1000 µm for a1, b1, c1, d1, e1, f1, g1, h1 and i1 and 200 µm for all other images

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