Gadolinium toxicity on sea urchin embryos of geographically and phylogenetically distant species

Gadolinium toxicity on sea urchin embryos of geographically and phylogenetically distant species C. Martino1,2, R. Chiarelli1, C. Costa2, D. Koop3, R. Scudiero4, M. Byrne3, V. Matranga2, M. C. Roccheri1 1 . Dept. STEBICEF, University of Palermo, Palermo, Italy 2 . IBIM CNR, Palermo, Italy 3 . Department of Anatomy and Histology, University of Sydney, NSW, Australia 4 . Dept. of Biology, University of Naples Federico II, Napoli, Italy chiara.martino@unipa.it Monitoring pollution in the marine ecosystems and understanding toxic effects is a key goal for environmental protection. Gadolinium (Gd) is a lanthanide metal whose chelates are employed as contrast agents for magnetic resonance imaging, and subsequently released into the aquatic environment. We investigated the effects of exposure to sub-lethal Gd concentrations on the development of four phylogenetically and geographically distant sea urchin species: two Mediterranean, Paracentrotus lividus and Arbacia lixula and two from Australia, Heliocidaris tuberculata and Centrostephanus rodgersii. Sensitivity to Gd greatly varied, with EC50 from 56nM to 132µM across the four species. Measures of the Gd and Ca content inside embryos showed a time/dose-dependent increase in Gd, in parallel with a reduction in Ca. In all the four species, we observed a general delay of embryo development at 24h post-fertilization and a strong inhibition of skeleton growth at 48h. RT-PCR gene expression analysis on P. lividus embryos showed the misregulation of several genes implicated in the skeletogenic gene regulatory network. Western blot analysis showed an increase of the LC3 autophagic marker at 24 and 48h. Confocal microscopy studies confirmed the increased number of autophagosomes and autophagolysosomes and showed no apoptotic induction. Results highlight that pollution assays based on only one species can be misleading with respect to hazard risk assessment and show the hazard of Gd in the marine environment, indicating that Gd is able to affect morphogenesis, stress response and gene expression in sea urchin embryos. In memory of our great colleague and scientist, Dr. Valeria Matranga.