Fig. 6.

C. calyptratus Fibroblast Growth Factor 8 (Fgf8) expression in the Apical Ectodermal Ridge. In wholemount in situ hybridization, the Apical Ectodermal Ridge expresses Fgf8 in the highly conserved pattern as seen in tetrapods (a-d) along the distal anteroposterior boundary of the limb. Fgf8 expression is maintained in the AER at stages where mesenchymal clefting of the autopodia has already commenced in both the hands and feet, though at a reduced amount prior to complete cleft formation (e-h)