Fig. 5
From: Mode of reduction in the number of pharyngeal segments within the sarcopterygians
Hoxb1 expression is spatially and temporally associated with the last formed pharyngeal pouch in both chick and catshark. Spatially and temporally dynamic expression of Hoxb1 is associated with the last formed pharyngeal pouch in both chick (a-d) and catshark (e-h) embryos. At stage 13 in the chick Hoxb1 expression is associated with the newly formed second pouch (a), while at stage 15 the expression of this gene is found in the newly formed third pouch (b). From stage 17 onwards, Hoxb1 expression is associated with the fourth pouch (c, d). In catshark embryos a similar spatially and temporally dynamic association between the expression of Hoxb1 and the last formed pouch is also seen, Thus while at stage 21, the expression of this gene is found at the fourth pouch (e), by stage 22 it is located to the fifth pouch (f) and by stage 23 and later with the sixth pouch (g, h). In all panels the position of the last formed pouch is highlighted by an arrow