Turtles as models for the maternal transfer of organic pollutants across reptile species, chemicals, and matrices

Maternal offloading of chemicals presents a first exposure for embryos during a critical window of sensitive early life development. We aimed to develop reptile-specific models to quantify this offloading. We fitted statistical models to data from two turtles (Malaclemys terrapin, Chelydra serpentina), and tested their ability to predict concentrations of organic pollutants in eggs across reptiles (turtles, snakes, crocodiles); legacy and emerging pollutants; and tissues (including blood as a low-invasive biomonitoring matrix). Maternal pollutant transfer could be quantified for several turtle species with a close alignment between lipid-normalised pollutant concentrations in mother and offspring. Concentrations were, on average, slightly lower in eggs than in females with higher transfer at higher maternal burdens. Predictions worked well between M. terrapin and C. serpentina and towards snakes and alligators where models transferred well across muscle, liver, and blood, and across several organic pollutant classes with some class-specific differences. Meanwhile, predictions did not match observations in sea turtles. Our results underscore the suitability of turtles as models to study the maternal pollutant transfer process, and the role of fresh and brackish water turtles as surrogate species to bridge the data gap in reptile ecotoxicology. Nevertheless, our study highlighted species-specific differences in maternal pollutant transfer. This cautions against blind extrapolation across species, and urges research into underlying mechanisms. We provide scientific tools (including a web application) to quantitatively predict embryonic exposure through transgenerational pollutant offloading as a prerequisite to assess risks for embryo toxicity, or, in reverse, to trace back maternal exposure from egg biomonitoring.