Impact of three phthalate esters on the sexual reproduction of the Monogonont rotifer, Brachionus calyciflorus

High concentrations of phthalates affect the early development of the sea urchin Paracentrotus lividus

The toxicity of three phthalates (PAEs) - butylbenzyl phthalate (BBP), diethyl phthalate (DEP), and di-(2-ethylhexyl) phthalate (DEHP) - was tested on the Mediterranean sea urchin Paracentrotus lividus. Fertilized eggs were exposed to environmental and high PAE concentrations for 72 h. The potential toxic effects on larval development and any morphological anomalies were then assessed to estimate PAEs impact. Environmental concentrations never affected development, while high concentrations induced toxic effects in larvae exposed to BBP (EC50: 2.9 ×103 µg/L) and DEHP (EC50: 3.72 ×103 µg/L). High concentrations caused skeletal anomalies, with a slight to moderate impact for DEP/DEHP and BBP, respectively. PAE toxicity was: BBP>DEHP>DEP. In conclusion, the three PAEs at environmental concentrations do not pose a risk to sea urchins. However, PAE concentrations should be further monitored in order not to constitute a concern to marine species, especially at their early developmental stages.

Butyl benzyl phthalate induced reproductive toxicity in the endoplasmic reticulum and oxidative stress in Brachionus plicatilis Müller, 1786

To study the adverse effects of butyl benzyl phthalate (BBP) on Brachionus plicatilis, rotifers were exposed to different BBP concentrations (0 [control], 0.001, 0.01, 0.1, and 1 mg/L). We measured the activities of the antioxidant enzymes superoxide dismutase, catalase, and reduced glutathione, which play a key role in detoxification, and the malondialdehyde content, which represents the level of lipid peroxidation. In addition, we investigated the effect of BBP on the submicroscopic structure and transcriptome of rotifer ovary cells. Our results showed that B. plicatilis exhibited a rapid oxidative stress response accompanied by a significant increase in superoxide dismutase enzyme activity. High BBP concentrations resulted in a significant decrease in malondialdehyde content, which indicated that BBP interferes with the lipid metabolism of rotifer cells. Our observations showed that the endoplasmic reticulum structure of rotifer ovary cells was severely damaged by BBP exposure. Transcriptomic data further demonstrated that oxidative stress and cellular sub-microstructural damage were associated with altered expression of functional genes related to rotifer redox regulation, biosynthetic processes, and cellular damage components. In conclusion, our study demonstrates that BBP triggers changes in antioxidant-related indicators in rotifers; this leads to activation of related genes and subsequent changes in intracellular signaling, which in turn triggers endoplasmic reticulum stress and ultimately leads to disruption of cell function and structure. These findings highlight the potential risks associated with BBP exposure and provide fundamental insights into its toxicological effects on marine invertebrates.

Seasonal distribution and ecological risk of phthalate esters in surface water and marine organisms of the Bohai Sea

The spatiotemporal variability and ecological risks related to 16 phthalate esters (PAEs) were investigated in surface water and marine organisms of the Bohai Sea. The average PAE concentrations in the surface water were 8.02, 4.53, and 3.16 μg L^-1 in spring, summer, and winter, respectively. Additionally, suspended particle matter was positive related to PAE content in seawater in spring and winter. The predominant PAEs in both water and biota were dimethyl phthalate (DMP), di-butyl phthalate (DBP), di-isobutyl phthalate (DIBP), and diethylhexyl-phthalate (DEHP). Because they do not exhibit long-distance migratory behavior, Chaeturichthys hexanema, Cynoglossus lighti, and Loligo japonica were good candidate indicator organisms for PAE pollution in Bohai Sea. The risk quotient method revealed that DIBP, DBP, and DEHP posed relatively greater risks to the aquatic system. This research establishes baseline data from which future management strategies to control PAEs in the Bohai Sea can be developed.

Evaluation of the spinal effects of phthalates in a zebrafish embryo assay

Phthalates (phthalate esters, PAEs) are commonly used as plasticizers and are emerging concerns worldwide for their potential influence on the environment and general public health. Thus, identification of the negative effects and involved mechanisms of PAEs is necessary. Herein, we found that embryonic exposure of zebrafish to di-(2-ethylhexyl) phthalate (DEHP) and di-butyl phthalate (DBP) significantly induced spinal defects, such as inhibited spontaneous movement at 24 h post-fertilization (hpf), spine curvature and body length decrease at 96 hpf. The transcriptional level of the genes that are related to the development of the notochord (col8a1a and ngs), muscle (stac3, klhl41a and smyd2b) and skeleton (bmp2, spp1) were significantly altered by DEHP and DBP at 50 and 250 μg/L, which might be associated with the observed morphological changes. Notably, DBP and DEHP altered the locomotor activity of zebrafish larvae at 144 hpf, which might be due to the abnormal development of the spine and skeletal system. In conclusion, phthalates caused spinal birth defects in zebrafish embryos, induced transcriptional alterations of the spinal developmental genes, and led to abnormal behavior.

Targeted impact of cyproterone acetate on the sexual reproduction of female rotifers

Monogonont rotifers constitute, depending on the moment of the year, most of the zooplankton in many freshwater ecosystems. Sexual reproduction is essential in the development cycle of these organisms as it enables them to constitute stocks of cysts which can withstand adverse environmental conditions and hatch when favorable conditions return. However, endocrine disrupting compounds (EDCs) can interfere with the reproduction of organisms. The present work aimed to investigate the effects of cyproterone acetate (CPA, anti-androgen and progestogen synthetic steroid) at 0.5 mg L^-1, on the sexual reproduction of Brachionus calyciflorus in a cross-mating experiment. Results show no impact on mixis whereas the fertilization rate and resting egg production were higher in females exposed to CPA (from embryogenesis to adult stage), regardless of the treatment applied to the males with which they were mating (i.e. males hatched from CPA-treated females or from control females). Moreover, neonate females which mothers has been exposed to 0.5 mg L^-1 CPA had more oocytes in their germarium than control neonates. Our results suggest that the effects of CPA observed are not related to toxicity but rather are consistent with an endocrine disruption-related impact, probably through disturbance of the mate recognition protein (MRP) production and through interference with a steroid receptor. Moreover, the absence of effect on mixis rate indicates that mixis induction on the one hand and mating process and resting production on the other hand are not controlled by the same hormonal pathways.

Reverse taxonomy applied to the Brachionus calyciflorus cryptic species complex: Morphometric analysis confirms species delimitations revealed by molecular phylogenetic analysis and allows the (re)description of four species

The discovery and exploration of cryptic species have been profoundly expedited thanks to developments in molecular biology and phylogenetics. In this study, we apply a reverse taxonomy approach to the Brachionus calyciflorus species complex, a commonly studied freshwater monogonont rotifer. By combining phylogenetic, morphometric and morphological analyses, we confirm the existence of four cryptic species that have been recently suggested by a molecular study. Based on these results and according to an exhaustive review of the taxonomic literature, we name each of these four species and provide their taxonomic description alongside a diagnostic key.

Prolonged exposure of di(2-ethylhexyl) phthalate induces multigenerational toxic effects in Caenorhabditis elegans

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is an emerging organic contaminant that has represented a risk for organisms present in the environment. However, there is still limited information regarding DEHP-induced multigenerational toxicity and the underlying mechanisms. In this study we investigated the multigenerational toxic effects including locomotive behaviors and reproduction upon prolonged DEHP exposure (from larval L1 to adult) and the underlying mechanisms in the nematode Caenorhabditis elegans. The multigenerational effects were examined over 6 generations (F0-F5) with only parental C. elegans (F0) was exposed to DEHP from larval L1 to adults (72h), and the subsequent offsprings (F1-F5) were grown under DEHP-free conditions. The results showed that prolonged exposure (72h) to various concentrations of DEHP caused dose-dependent locomotive impairments and reproduction defects in C. elegans and that a concentration of 0.2mg/L DEHP was enough to cause such sublethal effects. The results showed that after prolonged exposure to DEHP in the F0 generation, abnormal locomotive behaviors such as reduced body bends and head thrashes were observed from generations F0 to F5. Additionally, prolonged exposure to DEHP (20mg/L) in F0 significantly reduced total brood size in F0, and this parental exposure was sufficient to cause multigenerational reproductive toxicity in the offspring generations (F1-F5) as well. Furthermore, the expressions of reproduction-related genes such as vit-2 and vit-6 were down-regulated by about 20% until F3, and the expression of H3Kme2 demethylase, spr-5, was downregulated in F1 by about 40%. Results from this study demonstrate that prolonged exposure to DEHP only at F0 adversely affected reproduction and locomotive behaviors in C. elegans across generations and might be associated with inadequate vitellogenin production and malfunction of H3Kme2 demethylase. This study implies that parentally prolonged exposure to DEHP caused multigenerational defects in both reproduction and locomotive behaviors raising the potential health and ecological risk.

Characterization of Acute and Chronic Toxicity of DBP to Daphnia magna

As a commonly used phthalate compound, di(n-butyl) phthalate (DBP) is an emerging group of polyvinyl chloride plasticizers. The acute toxicity of DBP has been extensively studied using the aquatic indicator organism, Daphnia magna. However, little is known about chronic and transgenerational toxicity of DBP. In this study, acute LC₅₀ values were 3.04 mg/L (24 h) and 2.55 mg/L (48 h). Chronic toxicity tests in the case of maternal exposure to DBP revealed that DBP had negligible effects on growth and reproduction of F3 generation of D. magna, although the growth rate of body length and the intrinsic rate of increase were prominently reduced, to a pretty small extent. At specific concentrations, DBP generated beneficial effects on the parental generation of D. magna and no obvious impacts on the F1 generation. This study showed that maternal exposure to DBP did not cause any transgenerational effects on D. magna.