Developmental effects of siloxane exposure in zebrafish: A comparison study using laboratory‐mixed and environmental water samples

Abstract

Siloxanes are used in personal care, biomedical, and industrial products. Their worldwide use and persistence in the environment cause consistent exposure for both humans and aquatic animals. Two siloxane congeners, decamethylcyclopentasiloxane (D5; CAS 541-02-6) and octamethylcyclotetrasiloxane (D4; CAS 556-67-2), are among the most prevalent, with measurable levels in air, sediment, water, and biological samples. However, few studies have examined the impact of developmental (embryo/larva) exposure. To address this gap, we performed parallel experiments using wildtype zebrafish (Danio rerio). One set of experiments used laboratory-mixed individual solutions containing either D4, D5, or 2,4,6,8-tetramethylcyclotetrasiloxane (D 4 H ; CAS 2370-88-9); the other used environmental water samples containing a mixture of siloxanes, including D4 and D5. These samples were collected from Bladensburg Waterfront Park (BWP) a site along the Anacostia River, Washington, DC. In both experiments, zebrafish (24-48 h postfertilization, hpf) were exposed until 7 or 14 days (d)pf. Chronic exposure to D4, D5, orBWP water until 7 dpf caused stress-like behaviors and reduced swim velocities; anatomical differences were noted only in BWP-exposed larvae. At 14 dpf, BWP-treated larvae still showed slower swimming velocities and increased immobility; anatomical differences were no longer evident and thigmotactic behavior was reduced. D4 and D5-exposed larvae did not survive after 10 dpf. Larvae exposed to D 4 H showed no decreases in behavior or growth at either age. These results suggest early developmental sensitivity to siloxane exposure and point to the need to consider embryonic/ larval endpoints when assessing aquatic contaminants.

The Importance of Assessing Water Quality in Tributaries: A Case Study in an Urban Waterway Using Zebrafish (Danio rerio)

“…We previously showed that zebrafish larvae raised in water collected at more downstream locations of the Anacostia river (i.e., BWP and WNY) also showed increasing growth with age [32,33], consistent with the hypothesis that larval fish can survive and grow in the Anacostia river. However, specific growth differences for each sampling site were noted.…”

“…We previously reported the presence of siloxanes in water samples collected from both Washington Navy Yard (WNY) [33] and Bladensburg Waterfront Park (BWP) [32], two other locations along the Anacostia river. These sites are more downstream than PBS, located at the confluence of the northwest and northeast branches of the river (BWP) and close to the mouth of the river (WNY).…”

“…These compounds are known to alter fish behavior, growth, and/or survival [22][23][24][25][26][27][28][29][30][31]. Our recent work correlating water quality with larval fish growth and behavior using water collected from more downstream regions of the Anacostia [32,33] identified siloxanes, a component of personal care products, as a major contaminant at both sites. Larval zebrafish raised in these water samples displayed behavioral changes, with differences in growth and survival between the two sites.…”

Facile Synthesis of Benzimidazoles via Oxidative Cyclization of Acyclic Monoterpene Aldehyde with Diamines: Studies on Antimicrobial and in Vivo Evaluation of Zebrafish

“…Because no hatched embryos died, hatching rate success is regarded as a sensitive endpoint for the zebrafish embryo in toxicity experiments. It was found that the investigated chemicals resulted in a 48 h decrease in the hatching rate [37] …”

“…It was found that the investigated chemicals resulted in a 48 h decrease in the hatching rate. [37] When the dosage is increased to 1000 μg/mL, the percentages are only about (2-10 %, 1-3 %) and (14-32 %), respectively, Figure 4, when compared to the negative control for both (3d, 3g) and (1a), and the percentage gradually decreases from the order being (3g < 3d < 3e < 3k < 3e < 3j < 1a < 3f < 3a < 3i < 3l < 3b < 3h). Overall, 25 % of embryos with concentrations of (3a, 3b, 3f, 3i, 3l, 3h) of 750 μg/mL or greater are aberrant and have trouble developing into juvenile zebrafish (1a) showing in Table 7 that the latter compound is less toxic as it has a lower LC 50 value.…”