Summary of 17 chemicals evaluated by OECD TG229 using Japanese Medaka, Oryzias latipes in EXTEND 2016.

In June 2016, the Ministry of the Environment of Japan announced a program "EXTEND2016" on the implementation of testing and assessment for endocrine active chemicals, consisting of a two-tiered strategy. The aim of the Tier 1 screening and the Tier 2 testing is to identify the impacts on the endocrine system and to characterize the adverse effects to aquatic animals by endocrine disrupting chemicals detected in the aquatic environment in Japan. For the consistent assessment of the effects on reproduction associated with estrogenic, anti-estrogenic, androgenic, and/or anti-androgenic activities of chemicals throughout Tier 1 screening to Tier 2 testing, a unified test species, Japanese medaka (Oryzias latipes), has been used.

Summary of reference chemicals evaluated by the fish short-term reproduction assay, OECD TG229, using Japanese Medaka, Oryzias latipes.

Under the Organisation for Economic Co-operation and Development (OECD), the Ministry of the Environment of Japan (MOE) added Japanese medaka (Oryzias latipes) to the test guideline fish short-term reproduction assay (FSTRA) developed by the United States Environmental Protection Agency (US EPA) using fathead minnow (Pimephales promelas). The FSTRA was designed to detect endocrine disrupting effects of chemicals interacting with the hypothalamic-pituitary-gonadal axis (HPG axis) such as agonists or antagonists on the estrogen receptor (Esr) and/or the androgen receptor (AR) and steroidogenesis inhibitors. We conducted the FSTRA with Japanese medaka, in accordance with OECD test guideline number 229 (TG229), for 16 chemicals including four Esr agonists, two Esr antagonists, three AR agonists, two AR antagonists, two steroidogenesis inhibitors, two progesterone receptor agonists, and a negative substance, and evaluated the usability and the validity of the FSTRA (TG229) protocol.

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).

Lethal and sublethal effects of aniline and chlorinated anilines on zebrafish embryos and larvae.

Environmental risk assessments show increased attention to the sublethal effects of chemicals on aquatic organisms. The Organization for Economic Cooperation and Development (OECD) established the "Fish, Short-term Toxicity Test on Embryo and Sac-fry Stages" (OECD test 212) to predict lethal effects. It is still unclear, however, whether this test can predict sublethal effects.

Preliminary ecological risk assessment of butylparaben and benzylparaben -1. Removal efficiency in wastewater treatment, acute/chronic toxicity for aquatic organisms, and effects on medaka gene expression.

Butylparaben and benzylparaben, used as preservatives mainly in cosmetic products, have recently been found to be weakly estrogenic. Batch activated-sludge treatment and batch chlorination were carried out to roughly determine the removal efficiency of a wastewater treatment plant. Combining the removal efficiency with the estimated annual consumption and the unaltered excretion ratio, the maximum predicted environmental concentration (PEC) was estimated.

Feminization of Japanese medaka (Oryzias latipes) exposed to 17beta-estradiol: effect of exposure period on spawning performance in sex-transformed females.

Two groups of Japanese medaka (Oryzias latipes) were exposed to 17beta-estradiol (E2: 150ng/L, nominal concentration) for either a short-term exposure (STE: 0-31 days after fertilization (daf); egg-larval period) or a long-term exposure period (LTE: 0-81 daf; egg-adult period) and their subsequent spawning performance was compared in terms of fecundity, spawning time, and fertility. Most genetic males were transformed to phenotypic females by E2 following both short-term and long-term exposure, but spawning performance and gonad somatic index (GSI) of sex-transformed females (XY females) following long-term exposure were lower than those of sex-transformed females following short-term exposure and those of normal females (XX) in the control group. Sex-transformed females in the STE group and normal females possessed mature ovary, whereas most of the sex-transformed females in the LTE group possessed immature ovary, with most oocytes being in the pre-vitellogenic phase.

Feminization of Japanese medaka (Oryzias latipes) exposed to 17beta-estradiol: formation of testis-ova and sex-transformation during early-ontogeny.

Gonad histological changes were examined in Japanese medaka exposed to 17beta-estradiol (E2) during early-life stages. Two experiments were conducted at different concentrations of E2 (33.5 and 140.

Bioconcentration factor of relatively low concentrations of chlorophenols in Japanese medaka.

Bioconcentration factors (BCF) for pentachlorophenol (PCP) and 2,4-dichlorophenol (2,4-DCP) in Japanese medaka (Oryzias latipes) were determined at five different concentrations of the chemicals, between 0.1 and 10 microg/l (PCP), 0.3 and 30 microg/l (2,4-DCP), in the ambient water.

Seasonal changes in sex ratio, maturation, and size composition of fresh water snail, Sinotaia quadrata histrica, in Lake Kasumigaura.

Sinotaia quadrata histrica is a fresh water viviparous snail distributing from the Kanto region to Kyushu Island, Japan. About 7000 snails were collected in Lake Kasumigaura (L. Nishiura and L.