In female fish, no changes in the phenotypewere observed in the gonads
of fish fromeither the virgin- or marine-plastic treatment. In male
fish, we observed what appeared to be abnormal growth of germ cells
throughout the testicular tissue of one male fish from the marineplastic
treatment (Fig. 2) and no changes in fish from the virginplastic
treatment. As the proliferation of germ cells is one of the initial
steps of gametogenesis, normal germ cell proliferation is essential for
successful reproduction (Saito et al., 2007). In medaka, the proliferation