title: Phenylpyrazole insecticide fipronil induces male infertility in the estuarine meiobenthic crustacean Amphiascus tenuiremis.
abstract: Copepods are the most abundant arthropods on earth and are often the most important secondary producers in estuarine/marine food webs. The new GABA (gamma-aminobutyric acid)-disrupting insecticide fipronil (FP) induces unique sex-specific reproductive dysfunction in male meiobenthic copepods, leading to trans-generational population depression at environmentally realistic concentrations (0.63 microg/L). Using a newly developed 96-well microplate lifecycle bioassay, more than 700 individual Stage-I juveniles were reared to adulthood in as short as 12 days in only 200 microL of control (CTL) or 0.63 microg-FP/L seawater solution. Individual virgin male: female pairs were then cross-mated for all possible combinations within and across rearing treatments and allowed to mate for an additional 12 days in CTL or 0.63 microg-FP/L solution. FP at 0.63 microg/L caused no significant lethality to any mating combinations but evoked 73% or 89% inhibition of reproduction when FP-reared males were mated with either a control- or FP-reared female in FP solution, respectively. In contrast, when CTL-reared males were mated with FP-reared females in FP solution, there was no difference in reproductive success compared to FP-free controls. When FP-reared males were mated with either female group in FP-free solution, these mating pairs displayed a 3-day delay in time to brood sac extrusion but ultimately did reproduce. As fipronil (1) has a high K(ow), (2) is persistent in sediments where meiobenthic copepods live, and (3) has been detected in estuarine waters >0.7 microg/L, it may pose high risk to copepod production in estuarine systems.
authors.affiliation: Department of Environmental Health Sciences, Norman J. Arnold School of Public Health, University of South Carolina, Columbia, South Carolina 29208, USA.
authors.forename: Tawnya L
authors.initials: TL
authors.lastname: Cary
authors.forename: G Thomas
authors.initials: GT
authors.lastname: Chandler
authors.forename: David C
authors.initials: DC
authors.lastname: Volz
authors.forename: Spencer S
authors.initials: SS
authors.lastname: Walse
authors.forename: John L
authors.initials: JL
authors.lastname: Ferry
mesh_terms: D000818:Animals; D001681:Biological Assay; D033342:Copepoda / Q000502:physiology*; D005260:Female; D007248:Infertility, Male / Q000139:chemically induced* / Q000662:veterinary*; D007306:Insecticides / Q000633:toxicity*; D008297:Male; D011157:Population Dynamics; D011720:Pyrazoles / Q000633:toxicity*; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D007306:Insecticides; D011720:Pyrazoles; D014874:Water Pollutants, Chemical; C082360:fipronil