Lack of genotoxicity in Astyanax bimaculatus and Oreochromis niloticus of 17α-methyltestosterone used in fish hatcheries to produce male monosex populations

Abstract

ABSTRACT. 17α-Methyltestosterone (MT) is widely used in fish hatcheries of many countries to produce male monosex populations. Its genotoxic risk to fish species is not well known and studies in other in vivo models are still inconclusive. MT was tested for genotoxicity in the fish species Oreochromis niloticus (tilapia), a target species, and Astyanax bimaculatus (lambari), a native non-target species. Genotoxicity was evaluated by the micronucleus test (MN), nuclear abnormalities (NA), and comet assay using peripheral erythrocytes of both species after a 96-h exposure to MT at concentrations of 0.01, 0.1, and 1.0 mg/L in the water. At the lowest exposure level of 0.01 These effects were not observed in the comet assay. Chromatographic analysis of water samples collected from aquariums at the beginning and end of each experiment showed that MT was consumed during the 96-h exposure. At the highest level of exposure (1.0 mg/L), 81.69% of the hormone was consumed during the exposure period. The chromatogram showed that at the lowest concentration level of 0.01 mg/L, 99.56% MT was consumed by the end of the exposure period. Thus, exposure to MT did not cause genotoxicity in either fish species.

Effect of dosage of orally administered 17α-methyltestosterone on sex reversion of the yellowtail tetra Astyanax lacustris (Lütken, 1875)

“…The presence and increased frequency of micronuclei in erythrocytes is an indicator of genetic damage, likewise, nuclear alterations in erythrocytes may be an indicator of cytotoxic effect, both caused in fish exposed to environmental and chemical contaminants (Samanta and Dey, 2012;Ribeiro et al, 2014;Viana et al, 2018). Regarding the toxicity of MT in Astyanax, other studies observed an increased frequency of NA when adult individuals of another sister species, A. bimaculatus, were treated with feed supplemented with 60 mg/kg of this hormone for 28 days (Rivero-Wendt et al, 2013a) or by immersion with 1 mg for 96 hours (Rivero-Wendt et al, 2013b). In our study, three months after the end of the 30-day period of exposure to MT, only the highest doses of MT (40 and 60 mg MT/kg) showed a significant increase in NA frequency.…”

Molecular cloning, characterization, and expression profiles of androgen receptors in spotted scat (Scatophagus argus)

“…However, there are few studies on the sex reversal of S. argus. At present, sex reversal induced by exogenous steroid hormones is considered as an effective method that has been widely used in many fishes (He et al, 2003;Shi et al, 2010;Rivero-Wendt et al, 2013a;Gao et al, 2015). As the key factor mediating the effect of androgens, ARs have been shown to be involved in female to male sex change.…”