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. Author manuscript; available in PMC: 2014 May 1.
Published in final edited form as: Evol Dev. 2013 May;15(3):10.1111/ede.12035. doi: 10.1111/ede.12035

Fig. 2.

Fig. 2

Treatment of anuran embryos with a retinoic acid synthesis inhibitor results in the formation of a more derived/carnivore-like GD loop morphology. Xenopus laevis embryos were subjected to an acute chemical treatment with solvent control (ethanol, EtOH; A) or an RA synthesis inhibitor, DEAB (0.4 mM; B). The Xenopus GD loop (arrowhead; NF46) shifts posteriorly upon exposure to DEAB (B) and the final foregut anatomy appears similar to the normal morphology of Lepidobatrachus laevis (C; G 23; Although Xenopus NF46 is most equivalent to GS25, the relative anatomical topology of the foregut organs is already established by GS23 and is more easily visualized at this stage, i.e., before stomach expansion.). D: Effects on gut morphogenesis after treatment with small molecule inhibitors of retinoic acid synthesis (DEAB) or signaling (Ro-41-5253) are concentration dependent. The percentage of embryos with the derived/carnivore-like GD loop and organ placement (NF46) is indicated for different concentrations of each molecule. Embryos that exhibit severely disrupted development (e.g., massive edema, tail curvature) or abnormal, uninterpretable phenotypes not resembling either species are classified as “teratogenized.” Results are pooled from 5 different experiments. DMSO was used as the solvent control for Ro-41-5253. Ceratophrys cranwellii embryos were subjected to an acute chemical treatment with solvent control (EtOH; E) or an RA synthesis inhibitor, DEAB (0.5 mM; F). As observed in Xenopus, the Ceratophrys GD loop (arrowhead; GS25) shifts posteriorly upon exposure to DEAB (F) and the intestine (*) does not elongate, phenotypes remarkably similar to the morphological features found in Lepidobatrachus (C; GS23). The relative positions of the developing stomach (s), liver (L) and pancreas (p) are indicated, where visible.