Fig. 3

Bmp4 is expressed transiently during sterlet lateral line organ development. In situ hybridisation in sterlet for Bmp4. Black arrowheads indicate examples of neuromast regions; white arrowheads indicate examples of ampullary organ regions. For images of the trunk, boxes on low-power insets delineate the location of the trunk regions shown. (A,B) At stage 37, Bmp4 is not expressed in lateral line regions, although it is present around the nares and in fins and gill-filament primordia. (C,D) At stage 38, two dorsal spots of weak Bmp4 expression may represent sensory patches in the otic vesicle or early-forming neuromast primordia in the otic and supratemporal lines. Expression is also present in the gills, nares and barbel primordia. (E?G) At stage 40, expression is seen on the head in neuromast regions and fields of ampullary organ primordia (E,F; compare with Bmp5 and Cacna1d expression in Figure 1E?H). On the trunk, Bmp4 is expressed in primI and the most recently deposited neuromasts behind it, and in primII (G). (H?J) At stage 42, Bmp4 expression on the head has largely disappeared (H,I), apart from weak expression in the dorsal infraorbital field (arrowheads in I), although expression is still seen in gill filaments and barbels. On the trunk, expression is seen in primD and primII (J). (K?M) At stage 45, no lateral line expression is seen on the head (K,L), although weak expression persists in primD and primI on the trunk (M). Abbreviations: b, barbel; e, eye; f, fin; g, gill filaments; m, mouth; n, naris; prim, migrating lateral line primordium (primI, primary; primII, secondary; primD, dorsal); S, stage. Scale bar: 250 ?m.