Compounds altering fat storage in Daphnia magna

Abstract

The analysis of lipid disruptive effects in invertebrates is limited by our poor knowledge of the lipid metabolic pathways. A recent study showed that tributyltin activated the ecdysteroid, juvenile hormone and retinoic X receptor signaling pathways, and disrupted the dynamics of neutral lipids in the crustacean Daphnia magna impairing the transfer of triacylglycerols to eggs and hence promoting their accumulation in post-spawning females. Tributyltin disruptive effects correlated with lower fitness for offspring and adults. The present study aims to addresses effects of existing compounds on storage lipids in post-spawning females and their health effects. D. magna individuals were exposed 12 chemicals that included vertebrate obesogens (tributyltin, triphenyltin, bisphenol A, nonylphenol, di-2-ethylhexyl phthalate), other contaminants known to affect arthropods (pyriproxyfen, fenarimol, methoprene, emamectin benzoate and fluoxetine), as well as the natural hormones methyl farnesoate and 20-hydroxyecdysone. Reproductive effects were also assessed. Quantitative changes in storage lipids accumulated in lipid droplets were studied using Nile red staining, which showed a close relationship with whole organism levels of triacylglycerols. Ten compounds altered storage lipids in a concentration related manner enhancing (tributyltin, bisphenol A, methyl farnesoate, pyriproxyfen and 20-hydroxyecdysone) or decreasing (nonylphenol, fenarimol, emamectin benzoate, methoprene and fluoxetine) their levels in post-spawning females. Eight compounds that altered lipid levels also had detrimental effects on growth and/or reproduction.