Histopathological effects of the cyanobacterial toxin, Microcystin-LR on the exposed epithelial tissues of the amberwing spreadwing damselfly, Lestes eurinus, and the bloodworm, Chironomus riparius.

Cyanobacterial blooms have the potential to produce a variety of toxins, which can accumulate and become a major concerns for eutrophic and hypereutrophic systems. Toxicity studies have shown aquatic insects to be affected by these toxins. I examined the histopathological effects of Microcystin-LR on the epithelial tissues of the midgut of Amberwing Spreadwing Damselfly, Lestes eurinus, nymphs (Odonata:Lestidae) and the midgut of the Bloodworm Chironomus riparius (Diptera: Chironomidae). Nymphs and larvae were exposed to seven concentrations of Microcystin-LR, 0 μg L^-1, 1 μg L^-1, 10 μg L^-1, 20 μg L^-1, 35 μg L^-1, 60 μg L^-1, and 100 μg L^-1. Damselfly nymphs were exposed for six weeks and examined for histophathological damage at the end of dosing. Bloodworm larvae were exposed for two weeks, and also examined for histopathological damage at the end of dosing. The midguts were dissected and exposed to two florescent dyes, SYBR stain and propidium iodide and then examined for percent cell death using fluorescent microscopy. A regression analyses was run to determine the effects of increasing amounts of the toxin on these two types of tissues. The percent cell death was compare to the exposure concentrations to determine effects ofthe toxin on histopathological damage.