FIG. 6.

The onset of the first spawning is 47 days postfertilization (dpf). (A) Estimation of the sexual maturation of larval fish. The regression equation is displayed on the figure (R²=0.92). (B) A 46-dpf male (upper photograph) and female (lower photograph) zebrafish exhibiting sexually mature characteristics. The major secondary sex characteristic of a mature male fish is the body color, especially in the anal fin. The arrowhead in the upper photograph indicates the yellowish anal fin of the male compared with that of the female fish. The major sex characteristic of the female is a whiter body than that of the male fish. In addition, the larger belly (indicated by the arrow in the lower photograph) is also a typical female characteristic. The bar represents 10 mm. (C) One of the typical embryos from incross of 47-dpf zebrafish. The embryo exhibits the typical morphology at 1 dpf. The bar represents 1 mm. Color images available online at www.liebertpub.com/zeb