title: Developmental effects of fipronil on Japanese Medaka (Oryzias latipes) embryos.
abstract: Pesticides in urban runoff are a major source of pollutants in aquatic ecosystems. Fipronil, a phenylpyrazole insecticide, found in structural pest control products, turf grass control, and home pet flea medication, has recently increased in use and is commonly detected in urban runoff. However, little is known about the effects of fipronil on aquatic organisms at early developmental stages. Here, we evaluated toxicity of fipronil to embryos of Japanese Medaka (Oryzias latipes, Qurt strain) using a high-throughput 96-well plate toxicity test. Male and female embryos (<6 h post fertilization) were exposed to concentrations of fipronil ranging from 0.1 to 910 μg L-1for 14 days or until hatching. Embryos were subjected to gross and microscopic examinations of developmental adverse effects as well as transcriptome analysis using RNA-seq. Results indicated a positive dose-response in reduced hatching success, increased gross deformity (tail curvature) at a lowest-observed-effect concentration (LOEC) of 200 μg L-1and delayed hatching (∼1 day at the highest concentration, LOEC = 600 μg L-1). The transcriptome analysis indicated that fipronil exposure enhanced expression of titin and telethonin, which are responsible for muscle development. It is therefore possible that the formation of a tail curvature is due to asymmetrical overgrowth of muscle. Our results indicate that sub-lethal effects occur in embryonic stages of an aquatic vertebrate following exposure to high concentrations of fipronil, although no adverse effects at the highest published environmentally relevant concentration (6.3 μg L-1) were observed.
authors.affiliation: Aquatic Health Program, School of Veterinary Medicine, Department of Anatomy, Physiology, and Cell Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Wagner
authors.affiliation: Aquatic Health Program, School of Veterinary Medicine, Department of Anatomy, Physiology, and Cell Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA. Electronic address: tkurobe@ucdavis.edu.
authors.forename: Tomofumi
authors.initials: T
authors.lastname: Kurobe
authors.affiliation: Aquatic Health Program, School of Veterinary Medicine, Department of Anatomy, Physiology, and Cell Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Hammock
authors.affiliation: Aquatic Health Program, School of Veterinary Medicine, Department of Anatomy, Physiology, and Cell Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Chelsea H
authors.initials: CH
authors.lastname: Lam
authors.affiliation: Aquatic Health Program, School of Veterinary Medicine, Department of Anatomy, Physiology, and Cell Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Wu
authors.affiliation: Department of Entomology and UCD Comprehensive Cancer Center, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Natalia
authors.initials: N
authors.lastname: Vasylieva
authors.affiliation: Department of Entomology and UCD Comprehensive Cancer Center, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Shirley J
authors.initials: SJ
authors.lastname: Gee
authors.affiliation: Department of Entomology and UCD Comprehensive Cancer Center, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Hammock
authors.affiliation: Aquatic Health Program, School of Veterinary Medicine, Department of Anatomy, Physiology, and Cell Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Swee J
authors.initials: SJ
authors.lastname: Teh
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000187:drug effects*; D005260:Female; D007306:Insecticides / Q000633:toxicity*; D008297:Male; D009990:Oryzias / Q000196:embryology*; D011720:Pyrazoles / Q000633:toxicity*; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D007306:Insecticides; D011720:Pyrazoles; D014874:Water Pollutants, Chemical; C082360:fipronil
keywords: Developmental deformity; ELISA; Multi-model inference; RNA-seq