Microbiology
John Armstrong and George Malacinski have edited a fine book that compiles a cross section of developmental studies under way using the axolotl, and could be used both as an advanced undergraduate reference for general development and as a laboratory source for axolOTl maintenance.
Abstract
Historically, the foundations of experimental embryology can be traced back to the time between the first and second world wars. Hamburger (The Heritage of Experimental Embryology, Oxford Univ. Press, New York, 1988) does an admirable job of capturing this period, when a more holistic approach to embryology prevailed. During this period many of the present embryological concepts, such as induction, morphological field phenomena, determination, self-differentiation, and the "organizer" were developed and defined with concise embryological experiments using salamander embryos. Subsequent to the discovery of the structure of DNA by Watson and Crick during the fifties and the breaking of the genetic code during the sixties, embryology took a more reductionist and subcellular approach. The outlook shifted to a more programmatic emphasis on embryology, which was renamed "developmental biology." As emphasis in different hierarchial approaches shifted, there was also a change in favorite model organisms to study development. At the present time, favorite organisms to study development are Drosophila and Xenopus. These are popular because they are easily bred, embryos are accessible, they are relatively easy to manipulate and they develop quickly. Thus, quick answers to gene expression questions can be obtained. The axolotl, or Mexican salamander, Ambystoma mexicanum, has all of the above features, but it develops much more slowly. John Armstrong and George Malacinski have edited a fine book that compiles a cross section of developmental studies under way using the axolotl. They divide this book into three main parts: (1) natural history of the axolotl, (2) developmental studies using the axolotl, and (3) general and specific bits of information needed to rear and experiment with axolotls. The greatest bulk of the book consists of sixteen reviews of the stages and organs of axolotl development presently under investigation. These articles were written to emphasize the range of developmental studies using the axolotl and to underscore the advantages of using the axolotl for such studies. The articles are arranged in developmental order starting with gametogenesis and ending with an article on metamorphosis (or, in the case of the axolotl, "induced" metamorphosis). In general, the papers are clear and concise, and as a result they are informative to both the generalist and specialist. All cited references are at the end of the book rather than the end of each chapter. There are few editorial errors (e.g., "asses" instead of "assess," and two plates have their legends reversed), but the overall quality of the writing and photographs is very good. This book could be used both as an advanced undergraduate reference for general development and as a laboratory source for axolotl maintenance. With recent discoveries concerning homeobox genes in Xenopus and the correlation of the expression of these genes with segmentation events, the axolotl might become even more popular with regard to assessing the presumed function of these genes. A need for more slowly developing embryos will be required for experimental manipulation of developmental events to test tissue-causal relations that evoke homeobox gene expression. A return to the higher hierarchial levels of epigenetic interactions should also result in a switch in animal models back to more slowly developing embryos. GERALD W. EAGLESON, Biology, Loras College, Dubuque, Iowa