UBC Theses and Dissertations
Copper and nickel toxicity and metal loading capacity of larval haemolymph in Aedes aegypti, using a novel small volume laser ablation inductively coupled plasma mass spectrometry method Kotzeva, Lilia Dimitrova
Much of the current literature focuses on fish as models for waterborne metal toxicology, yet few studies examine invertebrate or insect metal toxicology. The present study examined copper and nickel waterborne toxicity in Aedes aegypti larvae. The 24-hour LC₅₀ for copper in fouth instar larval Aedes aegypti was 2.28 mmol L-¹ (95% C. I. 1.97, 2.67) and 4.63 mmol L-¹ (95% C. I. 4.25, 5.05) in the unfed and fed treatments respectively. The 24-hour LC₅₀ for nickel in fouth instar larval Aedes aegypti was 17.2 mmol L-¹ (95% C. I. 15.58, 18.66) and 27.2 mmol L-¹¹ 1 (95% C. I. 25.49, 29.11) in the unfed and fed treatments respectively. To determine the metal loading capacity of haemolymph following acute and chronic copper and nickel exposures, a novel laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was developed as an alternative approach to analysis of small-volume samples. Matrix matching of liquid samples and standards was achieved by using oiled TLC plates. Sample chamber orientation was assessed, and the orientation used was opposite to the manufacturer’s specified orientation, resulting in better ablation characteristics. The relationship between the volume and surface area of samples spotted on the TLC plates was found to be linear. The method was validated using a certified reference material (Seronorm). It was determined that the average peak height of the chromatographs were best for analysis, after spatial profiling established the area of the most stable analyte signal. Further, the analytical method was independent of volume, avoiding the need to accurately measure small-volume samples. Using the developed method, it was found that Aedes aegypti larvae have an innate level of copper in their haemolymph and can concentrate copper in their haemolymph when chronically exposed to a low concentration (0.25 mmol L-¹ -1 mmol L-¹). Conversely, larvae did not concentrate nickel in their haemolymph, and nickel was not found in control samples of haemolymph. Taken together, the data supports copper’s role as an essential metal and implies that nickel may not be an essential metal for larval Aedes aegypti.
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