Model Organisms in Developmental Biology I: Invertebrates

Abstract

The ability to understand developmental processes requires appropriate organisms. The field of genetics established the precedent of focussing research on a few reference or “model” organisms such as Drosophila or maize. Recent developmental biology has depended on a small number of organisms for much of its spectacular progress. This concentration of effort facilitates attempts to advance in the analysis of the basic processes down to the molecular level. On the other hand, there is no single organism which could be selected to study all fundamental events and aspects of development; for each embryonic development leads to a single particular species, and not to an animal in general. From the egg of Drosophila a fruit fly arises, not an insect in general, not a fish and not a human being. General principles are only recognized when the events of development are studied in several diverse organisms, which develop differently yet display some common features. In addition, laboratory work quickly reveals that even the best model organism exhibits, in addition to its particular advantages, specific disadvantages. Thus the zebrafish has transparent embryos but large-scale genetic studies require hundreds of aquariums and a staff of workers, and the mouse provides a wealth of developmental mutants but cannot be conveniently frozen for long-term storage.