Bioaccumulation and impact of maternal PFAS offloading on egg biochemistry from wild-caught freshwater turtles (Emydura macquarii macquarii)

ABSTR A C T Per-and polyfluoroalkyl substances (PFAS) are persistent synthetic contaminants that are pervasive in the environ -ment. Toxicity resulting from elevated PFAS concentrations in wildlife has been studied, yet evidence of their accumu-lation, developmental toxicity and maternal offloading in egg-laying species is limited. Here we show the maternal offloading of PFAS in freshwater short-necked turtles (Emydura macquarii macquarii) exposed to elevated PFAS and the resulting biological impact on oviducal eggs. Total PFAS concentrations were determined in serum from adult fe -males and harvested oviducal eggs collected from euthanised turtles exposed to low and high levels of PFAS and com-pared against turtle serum and eggs collected from a suitable reference site. Multi-omics assays were utilised to explore the biochemical impact of elevated PFAS on egg albumen, yolk and eggshell using a range of metabolomics, lipidomics, and proteomics techniques. Eggshells were also screened for metals by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Analysis of the serum collected from adult female turtles and their oviducal eggs demonstrated PFAS offloading and transference that is 1.6 and 5.3 times higher in the low and high PFAS impacted eggs, respec-tively, compared to maternal serum concentrations. Oviducal egg yolk comprised >90% of the bioaccumulated PFAS load. Multi-omic analysis of the dissected egg fractions illustrated PFAS impacted eggs are significantly elevated in purine metabolism metabolites, which are tied to potential biological dysfunctional processes. The yolks were sig-nificantly depleted in lipids and lipid quality tied to growth and development. The high PFAS impacted oviducal eggshells were lower in calcium, important developmental and immune response proteins, and higher in glycerophosphoethanolamines (PE) lipids and histidine metabolism metabolites that are tied to a weakened physical structure. Further investigation is needed to establish the rate of PFAS offloading and quantify the developmental impact on hatchling and hatchling success to fully demonstrate PFAS-developmental toxicity linkages.

Automated summary

This study reveals the maternal offloading of PFAS in short-necked turtles exposed to high concentrations of PFAS during the egg-laying process, and analyzes the biological impact of PFAS on the ovaries. The results show that PFAS can be transferred from the mother to the ovaries, resulting in higher concentrations of PFAS in the ovaries. In addition, the impact of PFAS on the ovaries is also manifested in changes in metabolites in the ovaries, as well as a decrease in lipid content and quality in the yolks, and a decrease in calcium content and weakened physical structure in the eggshells.