Journal
AQUATIC TOXICOLOGY
Volume 92, Issue 3, Pages 179-186Publisher
ELSEVIER
DOI: 10.1016/j.aquatox.2009.01.011
Keywords
Cadmium; Chironomus riparius; Cd2+-selective microelectrodes; Malpighian tubules; Cd secretion; Cd sequestration
Categories
Funding
- Natural Sciences and Engineering Research Council of Canada
- Canada Research Chair Program
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Many aquatic insects are very insensitive to cadmium in short-term laboratory studies. LC50 values for larvae of the midge Chironomus riparius are over 25,000 times the Criterion Maximum Concentration in the United States Environmental Protection Agency (U.S. EPA (2000)) species sensitivity distribution (SSD). Excretion or sequestration of cadmium may contribute to insensitivity and we have therefore examined cadmium transport by isolated guts and renal tissues of C. riparius larvae. Regional differences of Cd transport along the gut were identified using a Cd2+-selective microelectrode in conjunction with the Scanning lon-Selective Electrode Technique (SIET). Cd is transported into the anterior midgut (AMG) cells from the lumen and out of the cells into the hemolymph. The transport of Cd from the gut lumen to the hemolymph exposes other tissues such as the nervous system and muscles to Cd. The gut segments which remove Cd from the hemolymph at the highest rate are the posterior midgut (PMG) and the ileum. In addition, assays using an isolated Malpighian (renal) tubule preparation have shown that the Malpighian tubules (MT) both sequester and secrete Cd. For larvae bathed in 10 mu mol l(-1) Cd, the tubules can secrete the entire hemolymph burden of Cd in similar to 15 h. (C) 2009 Elsevier B.V. All rights reserved.
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