Embryonic Patterning: Segmentation; Compartments/Boundaries
Mesoderm-derived: Cardiovascular System; Somites; Limb Formation
Stage of Development: Embryo
This is a Stage 3 anole lizard (Anolis carolinensis) embryo. The optic cup (oc) and lens are well defined. Pigment is present at the posterior portion of the retina. The otic vesicle (ov), or future ear, is visible along the dorsal portion of the embryo. Dorsal/rostral to the otic vesicle is the future hindbrain (hb) and rhombencephalon. Ventral to the otic vesicle is the maxillary arch (ma), the mandibulary arch (md) and the branchial arches 2-4 (ba2-4). The maxillomandibular region will become the upper and lower jaw. The mandibulary arch and branchial arch are in the process of fusing. The heart (hr) will develop 3 chambers.
The telencephalon (te), diencephalon (di), and mesencephalon (me) are present but vaguely defined. Later, a telencephalon and diencephalon constriction will further separate these regions. The mesencephalon has increased in size, but is empty. Progenitor cells in the tailbud (tb) will enter the pre-somitic mesoderm (psm). Signaling networks and gradients will result in the formation of somites. There are 30-40 somites (s) that lie along the AP axis, which will become future vertebrae. The forelimb (fl) and hindlimb (hl) are elongating.
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