Fig. 6

Histology of adult zebrafish gut and swim bladder smooth muscle. A,B: The adult gut has a clear laminar structure of smooth muscle adjacent to the columnar epithelium (ce) consisting of an inner circular smooth muscle layer (csm), and an outer longitudinal smooth muscle layer (lsm). C,D: The adult swim bladder shows a slightly different cellular organization. In addition to an epithelial layer, there is an inner circular smooth muscle layer, and a mixed outer layer of radial smooth muscle (rsm), and longitudinal smooth muscle. For direct comparison between gut and swim bladder, A and C are presented at the same magnification, as are B and D. L, lumen.