. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. L Figure 4. Light micrographs of alcian blue staining (A-D) and camera lucida drawings (E-L) of cartilage elements at stage 39. The figure shows the cartilage elements of control larvae (A. E. and I) and larvae of embr>os exposed to retinoic acid (RA) at 5 x 10 ' M (B. F. and J), 10" M (C. G. and K). and 10'^ M (D, H. and L). Camera lucida drawings, which depict a dorsal view of the neurocranial cartilage (E-H) and a ventral view of pharyngeal/pectoral cartilage (1-L), show a progressive loss and malformation of cart
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. L Figure 4. Light micrographs of alcian blue staining (A-D) and camera lucida drawings (E-L) of cartilage elements at stage 39. The figure shows the cartilage elements of control larvae (A. E. and I) and larvae of embr>os exposed to retinoic acid (RA) at 5 x 10 ' M (B. F. and J), 10" M (C. G. and K). and 10'^ M (D, H. and L). Camera lucida drawings, which depict a dorsal view of the neurocranial cartilage (E-H) and a ventral view of pharyngeal/pectoral cartilage (1-L), show a progressive loss and malformation of cartilage to increasing concentrations of RA. Abbreviations for cartilage elements are listed m Table II, nc = notochord. Anterior is to the top. Scale bar (A) = 200 /jm (A-D) and (E) = 200 ^m (E-L). elements that could represent Meckel's cartilage (question marks. Fig. 4K) are often present, the morphological char- acteristics of these elements are incomplete, so positive identification is difficult. The basihyal, ceratohyals. and basibranchials are present but shorter and thicker (Fig. 4J and K): moreover, the number of ceratobranchials and hypobranchials that develop may vary. In less extreme cases anterior ceratobranchials are deleted (Fig. 4J and K). but the posterior elements develop. In the most extreme phenotypes. the ceratobranchials and hypobranchials do not form. The order of the ceratobranchials is distin- guished by their associations with the hypobranchials, their position relative to the pectoral girdle cartilage (which develops normally), and the presence of pharyn- geal teeth on the fifth ceratobranchial. At both concentra- tions of RA the epibranchials and pharyngobranchials are. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological
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