header logo image header logo text
Downloads Login
Research
General Information
ZIRC
This material is from the 4th edition of The Zebrafish Book. The 5th edition is available in print and within the ZFIN Protocol Wiki.

Stages During the Larval Period

Protruding-mouth stage (72 h):

Modified from: Kimmel et al., 1995. Developmental Dynamics 203:253-310. Copyright © 1995 Wiley-Liss, Inc. Reprinted only by permission of Wiley-Liss, a subsidiary of John Wiley & Sons, Inc.

EL = 3.5 mm, HTA = 25 degrees. The mouth is wide open and it protrudes anteriorly just beyond the eye.

The blade of the pectoral fin continues to expand, now extending posteriorly over most of the length of the diminishing yolk ball (Fig. 39F).

With Nomarski optics one can see gill slits, and prominent buds of developing gill filaments (Fig. 42A), sometimes including a blood vessel that carries circulating blood. Cartilage cells are distinctive in branchial arches 1, 2 (Fig. 42B), and 5 (Fig. 42C) but not in branchial arches 3 and 4. The primordium of the operculum extends posteriorly to cover the first or even the second branchial arch. The first visible bone in the zebrafish, the transversely-oriented cleithrum (Fig. 43) now appears, superficial to, and at the boundary between the first two myotomes. At this location, posterior to the otic vesicle and last pharyngeal arch, it extends ventrally into the pectoral region, where it serves as an anchor of the pectoral fin girdle. Nomarski optics are required to see it at this stage; in the young larva it becomes more prominent. Histological sectioning shows that the cleithrum is lined with osteoblasts, but these bone-forming cells are not easily visualized in the living embryo.

A side view with the dissecting microscope now reveals the whole length of the gut tract behind the pharynx.

Melanin accumulates in the patch overlying the swim bladder rudiment, making this region very distinctively darkened. Iridophore coverage of the eye has expanded to more than half its surface, except for radial stripes, where black melanin shows between the golden patches. Iridophores accompany each of the melanophore stripes, including the yolk stripe. Shortly, the latter will become a rather solid reflective band. The yellow cast of the whole dorsal aspect of the body has increased, so that the hue of the trunk now matches that of the head.

Circulation in the pharyngeal arch region is becoming more complex with the advent of gill filament development. A subintestinal vein (Reib, 1973) is variably present, ventral to the gut tract.

Day 4 stage (96h - 120hh):

A detailed description of this stage is not yet available.

Day 5 stage (120h - 144h):

A detailed description of this stage is not yet available.

Day 6 stage (144h - 168h):

A detailed description of this stage is not yet available.

Days 7-13 stage (7d - 13d):

A detailed description of this stage is not yet available.

Days 14-20 stage (14d - 20d):

A detailed description of this stage is not yet available.

Days 21-29 stage (7d - 13d):

A detailed description of this stage is not yet available.