Age- and sex-specific toxicity of nanosized and bulk zinc-oxide to the nematode, Panagrellus redivivus dataset

Description

Our study hypothesized that the toxicity of zinc oxide (ZnO) nanoparticles (NPs) on the nematode Panagrellus redivivus is influenced by particle size, nematode sex, and developmental stage. The data set comprises mortality rates of P. redivivus exposed to ZnO NPs at two nominal particle sizes (15 nm and 140 nm) across a range of concentrations (0 to 100 mg/L). Mortality was assessed for different developmental stages (juvenile stages J2, J3/J4, and adults) and separately for males and females to identify inter-age and inter-sex differences. ZnO NP suspensions were prepared and characterized before exposure experiments, with scanning electron microscopy (SEM) used to confirm particle size distribution and dissolution properties in exposure media. Contrary to initial expectations, 140 nm ZnO NPs exhibited higher toxicity than 15 nm ZnO NPs. The elevated toxicity of 140 nm ZnO is likely attributable to its irregular morphology and increased ion release compared to 15 nm ZnO. Male nematodes were more sensitive to 15 nm ZnO at higher concentrations, with significantly higher mortality rates compared to females. These results suggest that sex-based physiological differences, such as surface area-to-volume ratios and metabolic activity, may influence NP uptake and toxicity. Early larval stages (J2) showed the highest mortality across both particle sizes and concentrations. In contrast, older juveniles (J3/J4) and adults exhibited lower mortality rates, highlighting developmental stage as a critical factor in toxicity sensitivity. The observed toxicity patterns indicate that ZnO NP toxicity is not solely dependent on size but also on particle morphology and dissolution properties. The greater sensitivity of J2 larvae suggests that smaller body size and less developed physiological defenses may make early life stages more susceptible to nanoparticle stress. Additionally, the heightened sensitivity of males to 15 nm ZnO underscores the importance of considering sex-specific responses in toxicity assessments.

Steps to reproduce

Inter-age tests: A dose-response test system was chosen for the evaluation process, employing the bacterivore nematode, Panagrellus redivivus. The test system was modified from previously published methods (Hrács et al., 2018; Kiss et al., 2018; Ma et al., 2014). 100 random adult females were separated from a mixed population into a petri dish culture. Based on Mcinnis (1997) observation, we selected the fertilized females whom was thicker and had darker, more granular bodies due to the presence of eggs, embryos, and J1 larvae. The adult females were removed after a 20-hour incubation period, leaving only J2 larvae in the culture. The first synchronized age group was then allowed to develop on an oatmeal-kefir medium for 96 hours. At hour 76 of the experiment, the second synchronous culture was prepared. Twenty hours later, the length of one individual from each culture was measured to determine the developmental stages of the synchronized age groups (Fig. 1.). The 20-hour old culture consisted J2 larval stage with a body length of 250-350 μm, the 96-hour old culture consisted of J3 and J4 larvae with a body length of 350-850 μm. Then a mixture of adult males and females was separated from the strain culture (size: > 850 μm). These became the three age group of our experiment. The animals were transferred to a 96-well microplate (Bioster S.p.A., Italy). For each concentration, five individuals were placed in each unit for testing acute mortality in Milli-Q water test media with the animals; 160 µl of Milli-Q water was added to each well, followed by 160 µl of the prepared ZnO solutions. Four replicates for each concentration and a negative control (320 μl Milli-Q water) were applied. The microplates were incubated in a thermostat at 20 ± 1 C under dark conditions. Surviving specimens were counted at the end of the experiment under a transmission stereomicroscope (Olympus SZH 10). Following exposure, motionless individuals were considered dead. Inter-sex tests: For the tests above, samples were taken from the surface of the culture on the previously mentioned oatmeal medium and placed in a Milli-Q water dish. The separation of mature males and females from the mixed population was conducted by the morphological characteristics delineated by Bakonyi et al. (1995). Males are typically smaller than females. The vulval orifice in females is situated in the midline of the ventral side. In contrast, the male orifice is located at the posterior end of the body, where the short, curved mating spine is clearly visible. The sorting process was conducted using an automated pipette, which aspirated the animals with 30 μl of liquid. The sorted males and females were placed in a Milli-Q water dish. Subsequently, five individuals of each concentration, in four replicates, were transferred to a 96-well microtitration plate, resulting in a total of 140 individuals. From now on, the test was conducted using the same methodology as for the age group test.

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