Effects of silver nanoparticles on the freshwater snail Physa acuta: The role of test media and snails’ life cycle stage

Abstract

Silver nanoparticles (AgNPs) are widely used worldwide, most likely leading to their release into the environment and a subsequent increase of environmental concentrations. Studies of their deleterious effects on organisms is crucial to understand their environmental impacts. The freshwater snail Physa acuta was chosen to evaluate the potential deleterious effects of AgNPs and their counterpart AgNO , through water-only exposures. The toxicity of AgNPs is greatly influenced by medium composition. Thus, 2 media were tested: artificial pond water (APW) and modified APW (adapted by removing calcium chloride). Acute tests (96 h) were performed with juvenile and adult snails in both media to assess lethality, and egg mass chronic tests were conducted with APW medium only to assess embryo viability and mortality, carried out until 90% hatching success was reached in the control. Acute toxicity increased with decreasing shell length for both silver forms (ion and nanoparticle); that is, juveniles were more sensitive than adults. Different test media led to dissimilar median lethal concentrations, with chloride playing an important role in toxicity, most likely by complexation with silver ions, which would reduce the bioavailability, uptake, and toxicity of silver. Chronic tests showed that hatching success was more sensitive to silver in the ionic form than in the particulate form. Different forms of silver, exposure media, and life cycle stages led to different patterns of toxicity, highlighting an impairment in the snails' life cycle. Environ Toxicol Chem 2017;36:243-253. © 2016 SETAC.

Effects of AgNPs on the Snail Biomphalaria glabrata: Survival, Reproduction and Silver Accumulation

“…In agreement with some review studies, the size and the shape of NPs are key factors in the toxicity [2,21,22]. In addition, B. glabrata snails tested in the present study are about double the size of the organisms tested by Gonçalves et al [20], and all these aspects could explain the differences observed between the acute toxicity of AgNPs to P. acuta and B. glabrata .…”

“…In a similar study with the snail Physa acuta the authors observed low egg production in concentrations above 1 mg/L after 28 days of exposure, suggesting this concentration as the NOEC [23]. On the other hand, Gonçalves et al [20] observed the effects on hatching success of the snail P. acuta and found an EC50 of 0.09 mg/L of AgNPs. Several previous studies have already indicated that hatching delay is the main and most susceptible end point in chronic bioassays using snails [8,11,12], although this effect did not arise in the present investigation.…”

“…Then, the LC 50 at 10 days was calculated at 18.57 mg/L (13.93–24.77), close to that obtained by Govindasamy and Rahuman [19] with the fish Oreochromis mossambicus after 8 days of exposure. On the other hand, Gonçalves et al [20] found the LC 50 at 96 hours among adult snails, Physa acuta, at a concentration of 7.05 mg/L.…”

“…With regard to toxicity, values of silver found in snails were higher than the lethal values of both AgNPs [20] and Ag ionic [25]. In a field study in contaminated sites in England, Langston and Zhou [26] observed values of 2.2 to 22.0 µg/g of Ag in marine gastropod snails, Littorina littorea .…”

Toxicokinetics of pristine and aged silver nanoparticles in Physa acuta

“…P. acuta is an invasive snail found in lotic (riverine) and lentic (still water) ecosystems, representing a link between primary producers and predators in freshwater food chains, and can be vulnerable to contaminants in both sediment and water phases. 41 The toxicity of Ag-NPs to P. acuta has been previously studied. [41][42][43] Studies often evaluate accumulation only in soft tissues.…”