Fig. 1. Undifferentiated germ cells of rainbow trout, which are iteroparous, remain in the mature testes and ovulated ovaries, while undifferentiated germ cells of semelparous salmon (Chinook and Kokanee salmon) disappear with their maturation.

Left column, rainbow trout; middle column, Chinook salmon; right column, Kokanee salmon. Arrowheads indicate oogonia and spermatogonia in the ovary and the testis, respectively. The top and bottom pictures show hematoxylin and eosin (H&E)–stained and immunostained images using Vasa antibody, respectively. Scale bars, 20 μm.