. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RETINOIC ACID DEFECTS IN FUNDULUS EMBRYOS 285. Figure 2. Dorsal views of stage 29 embryos show the et't'ects ot retinoic acid (RA) on relative s\/x and head development. In control embryos (A) and embryos exposed to low concentrations of RA— 10 '"/W (B), 10"^ M (C). W M (D). and 10"'M (E), the eyes are lightly pigmented (arrows. A and E) and the telencephalic ventricle (tv. A and E) and optic tecta {ot. E) anterior to the hindbrain (hb, A and E) has expanded. Embryos exposed to 10"'' M RA lack retinal pig
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RETINOIC ACID DEFECTS IN FUNDULUS EMBRYOS 285. Figure 2. Dorsal views of stage 29 embryos show the et't'ects ot retinoic acid (RA) on relative s\/x and head development. In control embryos (A) and embryos exposed to low concentrations of RA— 10 '"/W (B), 10"^ M (C). W M (D). and 10"'M (E), the eyes are lightly pigmented (arrows. A and E) and the telencephalic ventricle (tv. A and E) and optic tecta {ot. E) anterior to the hindbrain (hb, A and E) has expanded. Embryos exposed to 10"'' M RA lack retinal pigment in the eyes (arrows, F). show abnormali- ties of the brain (asterisk. F) anterior to the hindbrain (hb. F), pectoral fin development (arrowhead. F), and an expansion of the visceral cavity (bracket, F). At 10^ AY RA embryos show abnormal pectoral fin development (arrows, G), and have severe malfomiations in the forebrain (fb. G). and an expanded visceral cavity (bracket, G). At 10"'M RA exposure, embryos consist only of a thin trunk (tr, H). Antenor is to the top. Scale bar = 200 greater than between .stages 25 and 29. The telen- cephalic ventricle (Fig. 2A. tv) of the forebrain wid- ened, the eyes are pigmented (arrows), and the optic tecta (ot) have enlarged posterior to the eyes. Embryos exposed to low concentrations (10"^-10 "'A/) of RA (Fig. 2B-E) are morphologically normal. In contrast, embryos treated with 10" Af RA have optic cups that are malformed and rotated anteriorly (arrows, Fig. 2F). The head has enlarged only over stage 25 embryos. The optic tecta are greatly reduced (asterisk), and the hindbrain (hb) region is shifted anteriorly. The visceral cavity is expanding and appears to be proportionately larger than in control em- bryos (bracket. Fig. 2F). Other defects also occur in ein- bryos (not shown). The otocysts contain smaller otoliths, and they are irregular in shape; the heart tube is attached by a thin
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