Impacts of the synthetic androgen Trenbolone on gonad differentiation and development – comparisons between three deeply diverged anuran families

Abstract

Using a recently developed approach for testing endocrine disruptive chemicals (EDCs) in amphibians, comprising synchronized tadpole exposure plus genetic and histological sexing of metamorphs in a flow-through-system, we tested the effects of 17β-Trenbolone (Tb), a widely used growth promoter in cattle farming, in three deeply diverged anuran families: the amphibian model species Xenopus laevis (Pipidae) and the non-models Bufo ( tes ) viridis (Bufonidae) and Hyla arborea (Hylidae). Trenbolone was applied in three environmentally and/or physiologically relevant concentrations (0.027 µg/L (10 −10 M), 0.27 µg/L (10 −9 M), 2.7 µg/L (10 −8 M)). In none of the species, Tb caused sex reversals or masculinization of gonads but had negative species-specific impacts on gonad morphology and differentiation after the completion of metamorphosis, independently of genetic sex. In H . arborea and B . viridis , mounting Tb-concentration correlated positively with anatomical abnormalities at 27 µg/L (10 −9 M) and 2.7 µg/L (10 −8 M), occurring in X . laevis only at the highest Tb concentration. Despite anatomical aberrations, histologically all gonadal tissues differentiated seemingly normally when examined at the histological level but at various rates. Tb-concentration caused various species-specific mortalities (low in Xenopus , uncertain in Bufo ). Our data suggest that deep phylogenetic divergence modifies EDC-vulnerability, as previously demonstrated for Bisphenol A (BPA) and Ethinylestradiol (EE2).

Agrochemicals disrupt multiple endocrine axes in amphibians

“…Testosterone and trenbolone acetate (a synthetic androgen) are used as growth promotants (to increase muscle growth and appetite) in animal agriculture. Exposure to trenbolone acetate has been shown to masculinize P. nigromaculatus (Li et al, 2014) and S. tropicalis (Olmstead et al, 2012), accelerate Müllerian duct regression in X. laevis (Haselman et al, 2016), induce adverse effects on gonadal morphology and differentiation in X. laevis, Bufo viridis, and Hyla arborea (Rozenblut-Kościsty et al, 2019). Although the reproductive effects of trenbolone acetate have been reported, cellular and molecular mechanism of action remains unknown.…”

New Insights into the Gametogenesis of Biomphalaria glabrata (Mollusca, Gastropoda, Pulmonata): Implications for Histopathological Assessment

“…The EDCs can decrease the reproduction, fertility, fecundity, hatching ratio, alter the synthesis and metabolism of hormones or their receptors, change the behavior and development, or induce histopathological alterations in the snail gonads [21][22][23][24][25]. The gonad (ovotestis) is a crucial organ for understanding the effects of EDCs on the aquatic environment in different species and may offer several histopathological biomarkers [26,27].…”

Endocrine disruption in teleosts and amphibians is mediated by anthropogenic and natural environmental factors: implications for risk assessment

“…These three species showed similar impacts on sexual differentiation among anurans in principle, but different vulnerabilities (e.g. due to deep phylogenetic divergence, differences in life style and history) [ 78 – 81 ], regardless of the great variation in genetic sex determination. Given the great species diversity and the phylogenetic divergence of many of the anuran species (which number over 7500), it can be expected that several of these may be differently susceptible to ED.…”