Main Page Dynamic Development
The Foundations of Developmental Biology
From Sperm and Egg to Embryo
Genetic Regulation of Development
Organizing the Multicellular Embryo
Generating Cell Diversity
Dynamic Development at a Glance
by Leon W. Browder and Becky Wong
Xenopus laevis, the South African Clawed Frog
Now that you have practiced using the Internet to obtain developmental biology
resources, you should be able to use that skill to explore the virtual world of
development, with The Virtual Embryo as your guide. We want to focus on two concepts
simultaneously throughout this course: the diversity of developmental programs and the
similarities among basic developmental processes. We're going to start with an overview of
amphibian development, using The Amphibian Embryology Tutorial, developed by Dr. Jeff
Hardin at The University of Wisconsin. At this time, we are not going to utilize the
entire tutorial, but we are going to focus on pages that describe the major early
developmental events. We shall return to other topics in this rich resource later.
Carefully examine the links below, but make sure you only look at the first page of that
link, unless otherwise instructed. When you have completed the page, use the
"back" button at the upper left-hand corner of the Netscape window (do not use
the "main menu" navigation bar at this point). You may return to this page by
pressing the "back" button on the upper left corner of the window or by
selecting Amphibian Development in the "Go" pull-down menu.
Welcome to the Amphibian
Embryology Tutorial: This link introduces you to this tutorial.
The highlighted links on this page take you to the glossary, which provides a definition
of that term. These links do not need to be accessed unless you require the
definition. The movie (oogen.MOV) shows the process of oogenesis, with the
animal pole at the top, and the yolk becoming localized in the vegetal hemisphere at the
The Full-grown Oocyte
There are six pages to be reviewed once you have entered this link. These pages are
accessed by clicking on the red arrow symbol at the top of this page. There is a
movie to be viewed on the Radial vs. Spiral Cleavage page (rad_spir.mov).
There are 17 pages to be studied. Stop after "The Relationship between Deep DIMZ
and Other Tissue". Again, use the red arrow symbol at the top of the page to take you
to the next page. To get back to this page, use the "back" button on
Netscape or use the "Go" command. Consult your textbook for additional
details on gastrulation.
- Introduction: Movie-nieuwkoop2.mov. This movie shows
gastrulation happening from the vegetal pole view. The cells of the outer layer
envelops the yolk cells of the lower half. Midway through this movie, the blastopore
is formed, and gastrulation continues.
- Morphogenic Movements
- More Morphogenic Movements
- Fate Mapping: This link requires for you to review the highlighted numbers
1-4 to trace how the vital dyes were used to follow the movements of cells as gastrulation
- Gastrulation Time-Lapse: Movie-xlgast.mov. Compare this movie
to the nieuwkoop2.mov movie; these two movies show the same processes, but in
- Sagittal View: Movie-wholegas.mov. Note the movement of the
yolk within the gastrula as convergence and extension by the outer cells form the
- Surface Fate Map: Movie-superfic.mov. Note the yellow ectoderm
invaginates as the presumptive epidermis covers the outer gastrula.
- Deep Fate Map: Movie-deepmap.mov. Notice the movement of the
leading edge mesoderm.
- Fate Maps of Urodeles vs. Xenopus
- Epiboly of the Animal Cap
- Apical Constriction of Bottle Cells: Click on the boxes the look at the the
three views of the bottle cells.
- 1. Onset of apical constriction
2. Blastoporal groove
3. Rolling of blastoporal lip
- DIMZ: Movie-dimx2.mov.
- Relationship Between Deep DIMZ and Other Tissue: Movie-i_nimz.mov.
We shall examine a dorsal view of a neurula-stage embryo. Note the distinct nature of the
"notoplate" of the neural tube, which is also known as the "floor
plate". It is anchored to the notochord, which is located just below it.
Time-lapse: Movie-keller_gast.mov. This movie begins the same as xlgast.mov
(gastrulation time-lapse movie), BUT the process advances through to neurulation.
Meanwhile, much has been happening internally. We shall be examining internal
morphogenesis in more detail later. However, to give you a feel for the internal
morphology of the embryo, we shall now examine cross-sections of the Rana embryo at
a stage that is roughly comparable to stage 23 in Xenopus. Initially, you should study the embryo in
depth by examining the material prepared by Dr. Steven Scadding at The University of
Guelph at his Web site, Developmental Biology ONLINE. Read his home page CAREFULLY
as it instructs you on how to navigate his site. Click "Go to the site"
icon to view the 37 photographs and familiarize yourself with the new terminologies.
Now, you should examine a video of the 4mm frog embryo (produced by
Dr. Laurie Iten, Purdue University). The video can be played both forward and backward and
can be stopped at any point. You should navigate through the embryo to get a feel for the
structural continuity.The cross-sections are shown sequentially, beginning anteriorly and
moving toward the rear end. You can manipulate the video so that you can examine any
region of the embryo in more detail.