Embryogenic staging of fugu, Takifugu rubripes, and expression profiles of aldh1a2, aldh1a3 and cyp26a1

Fugu (Takifugu rubripes) has contributed as an ideal model organism for understanding the structure and evolution of vertebrate genomes, but also has potential as a good model organism for developmental biology because of the availability of the genome information. However, there is no comprehensive report describing the developmental stages, which is fundamental data for developmental biology. Here we describe a series of stages of the embryonic development of fugu during the first 8 days after fertilization, i.e. from fertilization to hatching. We define seven periods of embryogenesis - the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. Stages subdividing these periods are defined based on morphological characteristics. In addition, as a model experiment of gene expression analysis using this staging series, we performed in situ hybridization of aldh1a2, aldh1a3 and cyp26a1 that play regulatory roles in retinoic acid (RA) metabolism essential for embryogenesis. This report provides fundamental information on fugu embryogenesis, which is anticipated to facilitate the use of fugu as a model organism for developmental studies.