Dynamic Development

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

Overview of Amphibian Development

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.

Oogenesis:  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 bottom.

The Full-grown Oocyte


Cleavage:  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). 

Gastrulation:  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 proceeds.
  • Gastrulation Time-Lapse:  Movie-xlgast.mov.  Compare this movie to the nieuwkoop2.mov movie; these two movies show the same processes, but in different perspectives.
  • Sagittal View:  Movie-wholegas.mov.  Note the movement of the yolk within the gastrula as convergence and extension by the outer cells form the blastopore.
  • 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.

Neurulation:  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.

Neurulation 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.

Dynamic Development at a Glance
Main Page Dynamic Development

Dynamic Development is a Virtual Embryo learning resource.

This material may be reproduced for educational purposes only provided credit is given to the original source.
Leon Browder & Laurie Iten (Ed.) Dynamic Development
Last revised Tuesday, July 28, 1998