Steroid androgen 17α-methyltestosterone induces malformations and biochemical alterations in zebrafish embryos

• 17α-methyltestosterone (MT) is used in aquaculture for sex reversion of female fish.
• Risks to non-target organisms and aquatic environments are mostly unknown.
• MT induced biochemical and developmental alterations in zebrafish embryos.
• MT inhibited Vitellogenin like-proteins at the lowest concentration tested (4 μg/l).
• Vitellogenin depletion in embryos may compromise the normal life cycle of fish.

The synthetic androgen 17α-methyltestosterone is widely used in fish aquaculture for sex reversion of female individuals. Little is known about the amount of MT residues reaching the aquatic environment and further impacts in non-target organisms, including fish early-life stages. Thus, in this work, zebrafish embryos were exposed to two forms of 17α-methyltestosterone: the pure compound (MT) and a formulation commonly used in Brazil (cMT). For MT, a 96 h-LC50 of 10.09 mg/l was calculated. MT also affected embryo development inducing tail malformations, edemas, abnormal development of the head, and hatching delay. At biochemical level MT inhibited vitellogenin (VTG) and inhibited cholinesterase and lactate dehydrogenase. cMT elicited similar patterns of toxicity as the pure compound (MT). Effects reported in this study suggest a potential environmental risk of MT, especially since the VTG effects occurred at environmental relevant concentrations (0.004 mg/l).