Effects of triphenyltin on reproduction in Japanese medaka (Oryzias latipes) across two generations.

Triphenyltin (TPT) is an organotin compound used in marine anti-fouling coatings to prevent the attachment and growth of marine organisms, and it has negative effects on aquatic organisms. TPT is still detected at low concentrations, although its use has been prohibited at least in the European Community and is restricted in Japan as well. Studies using Japanese medaka (Oryzias latipes) indicate that TPT has the potential to inhibit reproduction.

Medaka extended one-generation reproduction test evaluating 4-nonylphenol.

The medaka extended one-generation test (MEOGRT) was developed as a multigenerational toxicity test for chemicals, particularly endocrine-disrupting chemicals. Briefly, 3 generations of Japanese medaka (Oryzias latipes) are exposed to a chemical over a 20-wk period: 3 wk in the parental generation (F0), 15 wk in the first generation (F1), and 2 wk in the second generation (F2). The present study reports the first MEOGRT results concerning branched isomer mixtures of 4-nonylphenol (NP).

Development of an in vivo anti-androgenic activity detection assay using fenitrothion in Japanese medaka (Oryzias latipes).

The effects of endocrine disruptors, including anti-androgenic chemicals, on aquatic environments have received increased attention in recent years. Currently, the method used to screen chemicals for anti-androgenic activity is called the androgenized female stickleback screen, and it was established by the Organization of Economic Cooperation and Development in 2011 using the three-spined stickleback. However, screening chemicals for anti-androgenic activity has yet to be established using Japanese medaka.

Chronic toxicity of an environmentally relevant mixture of pharmaceuticals to three aquatic organisms (alga, daphnid, and fish).

Principles of concentration addition and independent action have been used as effective tools to predict mixture toxicity based on individual component toxicity. The authors investigated the toxicity of a pharmaceutical mixture composed of the top 10 detected active pharmaceutical ingredients (APIs) in the Tama River (Tokyo, Japan) in a relevant concentration ratio. Both individual and mixture toxicities of the 10 APIs were evaluated by 3 short-term chronic toxicity tests using the alga Pseudokirchneriella subcapitata, the daphnid Ceriodaphnia dubia, and the zebrafish Danio rerio.

Fish multigeneration test with preliminary short-term reproduction assay for estrone using Japanese medaka (Oryzias latipes).

The most potent chemicals potentially causing adverse effects on fish species are estrogens in human waste.Sewage is a source of these estrogens and it is difficult to reduce. In particular, although the bioactivity of estrone is estimated to be about half of that of estradiol, multiple studies report that more than 100 ng l(–1) of estrone can be detected in urban rivers, including discharges from sewage treatment works; approximately two times as high as estradiol.

Verification of responses of Japanese medaka (Oryzias latipes) to anti-androgens, vinclozolin and flutamide, in short-term assays.

Various testing methods for the detection of the endocrine disruptive activities of chemicals have been developed in freshwater fish species. However, a few relatively easier specific methods for detecting anti-androgenic activities are available for fish. The aim of this study was to verify the papillary process in Japanese medaka (Oryzias latipes) as an indicator of the anti-androgenic activity of chemicals.