title: Chronic exposures to monomethyl phthalate in Western clawed frogs.
abstract: Polymer flexibility and elasticity is enhanced by plasticizers. However, plasticizers are often not covalently bound to plastics and thus can leach from products into the environment. Much research effort has focused on their effects in mammalian species, but data on aquatic species are scarce. In this study, Western clawed frog (Silurana tropicalis) embryos were exposed to 1.3, 12.3, and 128.7mg/L monomethyl phthalate (MMP) until the juvenile stage (11weeks) and to 1.3mg/L MMP until the adult stage (51weeks). MMP decreased survival, hastened metamorphosis, and biased the sex ratio toward males (2M:1F) at the juvenile stage without altering the expression of a subset of thyroid hormone-, sex steroid-, cellular stress- or transcription regulation-related genes in the juvenile frog livers. At the adult stage, exposure to MMP did not have significant adverse health effects, except that females had larger interocular distance and the expression of the heat shock protein 70 was decreased by 60% in the adult liver. In conclusion, this study shows that MMP is unlikely to threaten amphibian populations as only concentrations four orders of magnitude higher than the reported environmental concentrations altered the animal physiology. This is the first complete investigation of the effects of phthalates in a frog species, encompassing the entire life cycle of the organisms.
authors: Chemistry and Chemical Engineering Department, Royal Military College of Canada, Kingston, ON K7K 7B4, Canada.
authors: Justine
authors: J
authors: Mathieu-Denoncourt
authors: Wildlife and Landscape Science Directorate, Environment Canada, Burlington, ON L7S 1A1, Canada.
authors: Shane R
authors: SR
authors: de Solla
authors: Chemistry and Chemical Engineering Department, Royal Military College of Canada, Kingston, ON K7K 7B4, Canada. Electronic address: valerie.langlois@rmc.ca.
authors: Valerie S
authors: VS
authors: Langlois
mesh_terms: D000818:Animals; D005260:Female; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D008297:Male; D008675:Metamorphosis, Biological; D010795:Phthalic Acids / Q000737:chemistry*; D012098:Reproduction; D013963:Thyroid Hormones / Q000378:metabolism*; D014982:Xenopus laevis / Q000002:abnormalities*
chemical_list: D012739:Gonadal Steroid Hormones; D010795:Phthalic Acids; D013963:Thyroid Hormones; C517284:monomethyl phthalate
keywords: Metamorphosis; Plasticizers; Reproduction; Sex steroids; Silurana tropicalis; Thyroid hormones