Reproductive and endocrine-disrupting toxicity of Microcystis aeruginosa in female zebrafish

Abstract

Microcystis aeruginosa, a primary species in cyanobacterial blooms, is ubiquitously distributed in water. Microcystins (MCs) purified from M. aeruginosa can exert reproductive toxicity in fish. However, the effects of M. aeruginosa at environmentally relevant levels on the reproductive and endocrine systems of zebrafish are still unknown. The present study investigated the reproductive and endocrine-disrupting toxicity of M. aeruginosa on female zebrafish (Danio rerio) by short-term exposure (96 h). After exposure, marked histological lesions in the liver or gonads, such as nuclear pyknosis and deformation, were observed, and the fertilization rate and hatchability of eggs spawned from treated females were both significantly lower than they were in females in the control group, suggesting the possibility of transgenerational effects of M. aeruginosa exposure. Moreover, M. aeruginosa exposure decreased the concentration of 17β-estradiol (E2) and testosterone (T) in female zebrafish. Interestingly, the vtg1 transcriptional level significantly decreased in the liver, whereas plasma vitellogenin (VTG) protein levels increased. The present findings indicate that M. aeruginosa could modulate endocrine function by disrupting transcription of hypothalamic-pituitary-gonadal-liver (HPGL) axis-related genes, and impair the reproductive capacity of female zebrafish, suggesting that M. aeruginosa causes potential adverse effects on fish reproduction in Microcystis bloom-contaminated aquatic environments.