This invention relates to a see-through medaka deficient in iridophores, melanophores, xanthophores and leucophores; a see-through medaka deficient in iridophores, melanophores and xanthophores, and whose sex can be identified by the presence or absence of leucophores and/or a DNA marker; and a see-through medaka wherein a specific organ is allowed to produce luminescence by introducing a hybrid gene being a fusion of a promoter of a gene expressing specifically in that organ and a coding region of a gene encoding a fluorescent protein, as well as a method of producing for each see-through medaka as mentioned above.
