title: Effects of exposure to high concentrations of waterborne Tl on K and Tl concentrations in Chironomus riparius larvae.
abstract: Thallium (Tl) is a non-essential metal which is released into the environment primarily as the result of anthropogenic activities such as fossil fuel burning and smelting of ores. The ionic radius of monovalent Tl⁺ is similar to that of K⁺ and Tl⁺ may thus interfere with K⁺-dependent processes. We determined that the acute (48 h) lethal concentration where 50% of the organisms do not survive (LC₅₀) of Tl for 4th instar Chironomus riparius larvae was 723 μmol L⁻¹. Accumulation of Tl by the whole animal was saturable, with a maximum accumulation (Jmax) of 4637 μmol kg⁻¹ wet mass, and K(D) of 670 μmol Tl l⁻¹. Tl accumulation by the gut appeared saturable at the lowest four Tl concentrations, with a Jmax of 2560 μmol kg⁻¹ wet mass and a K(D) of 54.5 μmol Tl l⁻¹. The saturable accumulation at the gut may be indicative of a limited capacity for intracellular detoxification, such as storage in lysosomes or complexation with metal-binding proteins. Tl accumulation by the hemolymph was found to be linear and Tl concentrations in the hemolymph were ~75% of the exposure concentration at Tl exposures >26.9 μmol L⁻¹. There was not a significant decrease in whole animal, gut or hemolymph K during exposure to waterborne Tl at any of the concentrations tested (up to 1500 μmol L⁻¹). The avoidance of hypokalemia by C. riparius larvae may contribute to survival during acute waterborne exposures to Tl.
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. Electronic address: belowir@mcmaster.ca.
authors.forename: Ryan
authors.initials: R
authors.lastname: Belowitz
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. Electronic address: leonarem@mcmaster.ca.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Leonard
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. Electronic address: odonnell@mcmaster.ca.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Donnell
mesh_terms: D000818:Animals; D002170:Canada; D002683:Chironomidae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure / Q000009:adverse effects; D041981:Gastrointestinal Tract / Q000737:chemistry / Q000378:metabolism; D006458:Hemolymph / Q000737:chemistry / Q000378:metabolism; D007408:Intestinal Absorption; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D007928:Lethal Dose 50; D011188:Potassium / Q000032:analysis / Q000378:metabolism; D013054:Spectrophotometry, Atomic / Q000662:veterinary; D013793:Thallium / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics / Q000633:toxicity*; D014018:Tissue Distribution; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D013793:Thallium; D011188:Potassium
keywords: Atomic absorption spectroscopy; Chironomus riparius; Gut; Hemolymph; LC(50); Potassium; Thallium; Whole Animal