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Fig. 1 | EvoDevo

Fig. 1

From: Formation and subdivision of the head field in the centipede Strigamia maritima, as revealed by the expression of head gap gene orthologues and hedgehog dynamics

Fig. 1

Expression of SP5/btd in early Strigamia development. All panels show ventral views, except (c), which is a lateral view. a (stage 2.1) A broad ring of SP5/btd expression surrounds the uniform blastoderm. b (stage 2.2, early) SP5/btd expression lies at the transition between the single layered blastoderm in the anterior and denser (multi-layered) nuclei in the posterior. c (stage 2.2, early) Lateral view of similar staged embryo as in (b): the ring of SP5/btd expression has opened dorsally. d (stage 2.2, late) The initial ring of SP5/btd expression has condensed to a domain situated at the posterior of the emerging head field; this domain (green arrowhead) marks the future antennal and intercalary tissue. Bilateral (ocular) expression domains (circled, white arrowheads) emerge anteriorly adjacent to this domain. e (stage 2.3, early) Ocular domains detach from the more posterior domain. A dashed line marks the anterior margin of the condensed head field. f (mid-stage 2.3) The head primordium is now clearly defined; the anterior medial region (double headed arrow) occupies the anterior-most part of the head. Mandibular SP5/btd expression appears posterior to the antennal/intercalary SP5/btd domain, which is still continuous. g (stage 3.1) The antennal and intercalary regions of SP5/btd expression have separated. h–j Enlargements of the ventral parts of embryos stained for SP5/btd and engrailed (en). h (stage 2.2) Early SP5/btd expression lies directly anterior to the first (intercalary) stripe of en expression. i (stage 2.2, late) Intercalary en expression is directly posterior to antennal/intercalary SP5/btd expression; the mandibular en stripe emerges more posteriorly. j (stage 2.3 early) Antennal en expression appears within the main SP5/btd domain. oc ocular, int intercalary, ant antennal, md mandibular

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