Abstract:

The lethal and sublethal effects of Roundup (active substance glyphosate herbicide on phantom midge (Chaoborus flavicans, Meigen, 1830) larvae were checked in the range of concentrations from 20 to 2000 μg/L, in the five-day long tests. The herbicide caused the mortality of insects, with the LC$_{50}$ values ranging from 357.2 to 120.9 μg of glyphosate/L, for one and five days, respectively. The correlation coefficient >0.9 indicated a strong positive correlation between the concentration of Roundup in water and the mortality of C. flavicans. Also, the LT50 values indicate the toxic activity of the herbicide for the larvae. Also, the reaction to mechanical stimuli was disturbed, in a dose-dependent manner. We also observed the altered vertical migration of midges within the water column. The microscopic observations revealed malformations in insect' morphology and anatomy. Among the most prominent changes were: altered body shape and lower density of chromatophores in air sacs. These changes are in tune with the microscopic observations. We conclude that Roundup 360 Plus herbicide may cause significant changes within C. flavicans populations, especially during long exposure. This, in consequence, may lead to a decline in the population of phantom midges, and next, affect the organisms at the other trophic levels.

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