Effects of DEHP on post-embryonic development, nuclear receptor expression, metabolite and ecdysteroid concentrations of the moth Spodoptera littoralis

Abstract

Di (2-ethylhexyl) phthalate (DEHP) is recognized in vertebrates as an Endocrine Disrupting Chemical (EDC). DEHP can alter steroid hormones production, development, reproduction and behavior in vertebrates. Only few studies investigated DEHP effects on insects. However, some recent studies on aquatic insects showed that DEHP could also act as an EDC by interfering with the signaling pathways of ecdysteroids, the main hormones involved in the control of insect postembryonic development and physiology. The aim of the study was to investigate (1) the fate of DEHP within a terrestrial insect species by exposing larvae to food containing a wide range of DEHP concentrations and (2) the effects of this chemical on their post-embryonic development and metamorphosis, by using a multi-level approach. DEHP was shown to be present both in larvae and resulting stages, with higher concentrations in chrysalises and adults than in larvae. DEHP concentrations also decreased at the end of the last larval instar, suggesting the metabolic transformation or excretion of this chemical during this time. Only the two highest DEHP doses induced higher insect mortality, whereas low and intermediate concentrations increased larval food consumption without affecting body weight. Metabolic profiles showed that in control insects, the last three days before metamorphosis correspond to a metabolic transition, but with time-dependent changes in treated insects. Interestingly, DEHP treatments also alter both hemolymphatic ecdysteroid titers and expression levels of ecdysteroid response genes. These results confirm that DEHP can alter insect post-embryonic development and metamorphosis, by interfering with ecdysteroid pathways.

Effects of DEHP on the ecdysteroid pathway, sexual behavior and offspring of the moth Spodoptera littoralis

“…Statistical analyses were performed using R 3. reflected in a discrepancy between the expected and measured amounts of DEHP in food. This contamination was also observed in our previous study (Aviles et al, 2019). We thus completed the previous analysis by measuring the DEHP content in more adults, including individuals that developed from larvae exposed to 443 ng/g and 676 ng/g DEHP (Fig 1A).…”

“…Insect rearing, treatment and tissue collection S. littoralis larvae were reared on a semi-artificial diet (Hinks and Byers, 1976) at 23°C and 60%-80% relative humidity under a 16:8 light:dark cycle until emergence. From the third larval instar until pupation (i.e., ~ 15 days), larvae were fed a semi-artificial diet containing different concentrations of DEHP (DEHP, PESTANAL® 36735, Sigma, France) as described in Aviles et al 2019. We tested six environmentally relevant concentrations (100 pg, 1 ng, 10 ng, 100 ng, 1 µg and 10 µg per gram of food) and two higher concentrations (500 µg and 5 mg per gram of food), with DEHP dissolved in ethanol (ethanol, absolute, PROLABO®, VWR, France).…”

“…All adult males and females were exposed during larval stages as previously described in Aviles et al (2019). Control larvae were reared with food containing only the solvent (500 µL of ethanol in 100 g of semi-solid food).…”

“…DEHP content was measured in males and females that developed from DEHP-contaminated larvae or control larvae as described in Aviles et al (2019). The insects were stored at -18°C, lyophilized and crushed in a mortar.…”

“…Several studies highlighted DEHP accumulation in cultivated plants with a range of concentration going from 0.1 to 4150 µg of DEHP per gram of plant or leaf (i.e. dry weight) and from 26.5 to 362 µg of DEHP per gram of peel and flesh of three fruits (Aviles et al, 2019). Herbivorous insects are likely to ingest DEHP when feeding on cultivated plants.…”