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Fig. 3 | BMC Biology

Fig. 3

From: Novel developmental bases for the evolution of hypobranchial muscles in vertebrates

Fig. 3

Shark Lbx1 and Lbx2 are expressed in distinct muscle primordium in the trunk. Transverse sections of S. torazame embryos at ac stage 27, df stage 28, and gi stage 29. a Expression of Lbx1 detected in the pectoral muscle precursor cells (arrows). b A serial section to a, Lbx2 is expressed in the ventral somite in the body wall. c At the pectoral fin level, Lbx2 is expressed in rectus abdominus muscle primordia (dotted bracket), which is not yet differentiated, as shown by the absence of MyHC staining (c). d, e Lbx1 is expressed in the pectoral fin muscle primordia (arrow) which is also stained with ZO-1 tight junction antibody. gi At stage 29, Lbx1 is expressed in the pectral fin muscle primordia which are still not differentiated. Expression of Lbx2 is no longer detectable. Muscle differentiation is observed only in the rectus abdominus (dotted bracket) but not yet in the fin (i). j, k At stage 32, muscle differentiation is observed in the appendicular (arrow in j) and median (arrow in k) fins. l At stage 29, Lbx1 is expressed in the muscle precursor cells in the dorsal median fin (arrow). Scale bars, a, d, g 0.1 mm; j, k 0.5 mm; l 0.05 mm

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