Meeting Abstract

P2.86  Saturday, Jan. 5  Maternal transfer of mercury and its redistribution in tissues of metamorphosing Xenopus laevis tadpoles ROCK, K.; BRADSHAW, E*; MAYER, M; SKEELS, M; SCHREIBER, A; St. Lawrence University; St. Lawrence University; St. Lawrence University; St. Lawrence University; St. Lawrence University aschreiber@stlawu.edu

Mercury (Hg) from industrial pollution is converted into its toxic organic form, methylmercury (MeHg), which bioaccumulates in aquatic wildlife. MeHg binds to cellular protein, and its sub-lethal effects include neurotoxicity, endocrine disruption, and immune suppression. Total Hg concentrations from amphibians living in Hg-rich wetland environments vary between 0.04 and 1.6 ug/gram tissue. Few laboratory studies using amphibian models have addressed dietary Hg uptake and distribution among different life history stages. After feeding adult females swordfish fillets (0.1 ug Hg/g fillet) for one month, total Hg levels increased from less than 0.01 to 2.5 ug/g in liver, and increased to 0.5 ug/g in ovaries. Interestingly, concentrations of total Hg in tadpole progeny (7d) of swordfish-fed females was 50-fold higher (0.5ug/g) compared with controls, suggesting that Hg is maternally transferred. To study how Hg distribution changes during metamorphosis, Nieuwkoop-Faber (NF) stage 54 tadpoles were raised for 30d on a diet of powdered swordfish, resulting in a 200-300 fold increase in total Hg by NF 57, with tail Hg (2.8 ug/g) significantly higher compared with body levels (1.9 ug/g). Interestingly, following metamorphosis the concentration of Hg increased abruptly by a further 2-3 fold (limb and body Hg levels were 6 and 4 ug/g, respectively), even though the tadpoles were not fed during this period. We attribute the abrupt rise in body Hg to transference of Hg from resorbing and condensing organs, such as the tail, gill, and gut, to proliferating organs like the brain and limbs. Therefore, metamorphosis may represent a critical period when tadpoles living in environments containing elevated Hg are particularly susceptible to its toxic effects.