Sex-related Embryotoxicity of Pulp Mill Effluent Extracts in Medaka (Oryzias latipes) Female Leucophore-free FLFII Strain.

The aim of this study was to evaluate the effects of exposure to Chilean pulp mill effluent extracts on developing post-fertilized medaka embryos before and after sex definition relative to sex steroids (testosterone and 17β-estradiol) and a wood phytoestrogen (beta-sitosterol). Our study included two waterborne semi-chronic exposure experiments, using 24hpf unknown-sex FLFII (female leucophore free) group and a second 72hpf FLFII phenotypic sex-identified group (male autofluorescence leucophore) strain medaka embryos. Chronic exposure of both FLFII strain embryo groups showed similar delay in time to hatch and decreased hatchability. Teratogenic responses such as vertebral malformation (fusion, incomplete formation and lack of vertebral formation process) and pericardial edema were observed in both experiments, with a high percentage related to FLFII fluorescent leucophore identified males. In addition, high mortality associated with severe malformations was observed in male and female embryos exposed to testosterone. Our research has demonstrated that exposure to Chilean mill effluent extracts caused severe male medaka embryotoxicity (post-fertilized embryos) before and after sex definition and, irrespective of the experimental group and effluent treatment, suggests partial removal following secondary treatment. Furthermore, differences in the severity and type of teratogenic effects with previous experiments (d-rR medaka strain), are associated with the unique phenotypes of this medaka mutant strain. This article is protected by copyright. All rights reserved.