Developmental Staging in Xenopus laevis

Preface

"The greatest progressive minds of embryology have not looked at hypotheses; they have looked at embryos." ~Jane Oppenheimer

"Theories come and theories go. The frog remains." ~Jean Rostand

Xenopus is at once elegantly simple and infinitely complex--I found it a wonder to study. My interest in Xenopus and development began in spring of 2001. At the time, being the precocious biology student that I was, I was enrolled in Developmental biology and Vertebrate Field Zoology (a mistake I was later to regret). In zoology, I was identifying birds through the use of field guides based on anatomical features. Meanwhile, in developmental biology I was struggling with the staging of Xenopus tadpoles. Out of my frustration arose my inspiration. I thought it would be a good idea if there were a pictoral atlas that could be used to aid students in identifying stages during tadpole development. The Nieuwkoop and Faber drawings were very detailed, but it was hard to know what anatomical characteristics to look for, and how important they were. I sat down with Dr. Lom and we came up with other advantages—reality, magnification and multiple perspectives. I began compiling photographs in the summer of 2001, but wasn’t able to organize them into a concrete format. The following year (in the spring of 2002) I was given the opportunity to complete the project as an independent study. This is the result of my labors. I have tried to remain faithful to the original text and create a resource that will be both accurate and efficient. It is my hope that students and researches alike will find use for this valuable resource. -Will Graham, '02

The South African clawed frog Xenopus laevis is widely used as a model organism in developmental biology because its transformation from zygote to tadpole can be easily observed in the laboratory. Since individual variation and temperature dramatically affect the developmental progression of ectotherms, Xenopus embryonic stages cannot be assigned chronologically. In 1956 Nieuwkoop and Faber published an illustrated and extensively annotated anatomical staging table that became the standard atlas for uniformly and consistently identifying Xenopus stages. In order to facilitate more accurate determination of Xenopus laevis embryonic stages, we have compiled a photographic atlas to accompany Nieuwkoop and Faber's illustrated staging table. This photographic atlas is the first comprehensive collection of digital images of Xenopus embryos detailing dorsal, ventral, and lateral perspectives of embryos at nearly every stage of development (stages 1-50). The photographs provide more representative depictions than do the original illustrations. Additionally, we have annotated the photographs with the most salient structural features described in Nieuwkoop and Faber's extensive text to assist in the identification of prominent anatomical features. We anticipate that this web-based photographic atlas will improve students' and researchers' abilities to identify Xenopus laevis stages more easily and accurately.

Digitized images and developmental data from Nieuwkoop and Faber (1994) Normal Table of Xenopus laevis (Daudin). Garland Publishing Inc, New York ISBN 0-8153-1896-0.

Digital images of drawings created by Matt Cockerill and Peter Vize from Xenbase http://www.xenbase.org/atlas/NF/NF-all.html Copyright © 1994 Pieter D. Nieuwkoop and J. Faber.

Digital photographs of Xenopus embryos and site design copyright of William Graham, '02 and Ian Willoughby, '03. All rights reserved. No portion of them can be used without prior expressed permission.

Some of our Xenopus embryo photographs appear in the book Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom by Sean Carroll (2005) on pg. 85.

updated 26 June 2005