Modified from: Kimmel et al., 1955. Developmental Dynamics 203:253-310. Copyright © 1995 Wiley-Liss, Inc. Reprinted only by permission of Wiley-Liss, a subsidiary of John Wiley & Sons, Inc.
By day 3 the hatched larva has completed most of its morphogenesis, and it continues to grow rapidly. Prominent changes during the next day include the inflation of the swim bladder and the continued anterior-dorsal protrusion of the mouth (Fig. 39G, H). During the same time the reflective strips of iridophores brighten and lengthen, the ventral yolk band extending in both directions. The gut tube drops more ventrally, where it can be seen more easily, and the yolk extension nearly empties. Whereas during the hatching period the embryo is usually at rest, the early larva gradually begins to swim about actively, and moves its jaws, opercular flaps, pectoral fins, and eyes. These developments produce swift escape responses, and herald respiration, the seeking of prey, and feeding.