STAGES OF EMBRYONIC-DEVELOPMENT OF THE ZEBRAFISH

We describe a series of Stages for development of the embryo of the ze brafish, Danio (Brachydanio) rerio. We define seven broad periods of e mbryogenesis-the zygote, cleavage, blastula, gastrula, segmentation, p haryngula, and hatching periods. These divisions highlight the changin g spectrum of major developmental processes that occur during the firs t 3 days after fertilization, and we review some of what is known abou t morphogenesis and other significant events that occur during each of the periods. Stages subdivide the periods, Stages are named, not numb ered as in most other series, providing for flexibility and continued evolution of the staging series as we learn more about development in this species. The stages, and their names, are based on morphological features, generally readily identified by examination of the live embr yo with the dissecting stereomicroscope. The descriptions also fully u tilize the optical transparancy of the Live embryo, which provides for visibility of even very deep structures when the embryo is examined w ith the compound microscope and Nomarski interference contrast illumin ation. Photomicrographs and composite camera lucida line drawings char acterize the stages pictorially. Other figures chart the development o f distinctive characters used as staging aid signposts. (C) 1995 Wiley -Liss, Inc.