Assessing Impacts of Insecticides on Different Embryonic Stages of the Nontarget Aquatic Insect Cheumatopsyche brevilineata (Trichoptera: Hydropsychidae)

Abstract

Although the egg of aquatic insects is one of the main life stages that can be exposed to contaminants in water, little is known about the detailed impacts of contaminants on eggs of aquatic insects. The present study aimed to clarify the vulnerable embryonic stages of the caddisfly Cheumatopsyche brevilineata exposed to 2 insecticides, etofenprox and diflubenzuron, which are severely harmful to aquatic insects, and to assess the effects of exposure duration on toxicity of etofenprox to the embryonic stage. Eggs obtained from laboratory culture of the insect were exposed to etofenprox for different periods (2, 4, 6, or 8 d) and at different embryonic stages. In experiments with diflubenzuron, eggs were exposed for 2 d at different embryonic stages. These insecticides did not kill the embryos during exposure, but they inhibited hatching post exposure. Diflubenzuron also induced morphological abnormalities of hatchlings and reduced their survival. The overall median lethal concentration (LC50overall) values varied significantly from 0.0560 to 5.19 μg/L for etofenprox among exposure durations and among embryonic stages, and from 0.442 to 2.89 μg/L for diflubenzuron between embryonic stages. The toxicity of etofenprox to the embryo was more dependent on the embryonic stage at the time of exposure than on the exposure duration. The vulnerable embryonic stage differed between the insecticides. Etofenprox more strongly inhibited hatching of embryos at later stages, whereas sensitivity to diflubenzuron was higher in the following order: stages E3 to E7 > stages E1, E2, and E8. The different responses of C. brevilineata embryos may be attributable to differences in insecticide mode of action and in functional development of insecticide target sites during embryogenesis. Environ Toxicol Chem 2019;38:1434–1445. © 2019 SETAC

Chemical Aspects of Human and Environmental Overload with Fluorine

“…The same drug also resulted in reduced growth rate for tadpoles, resulting in smaller frogs at a disadvantage for predator evasion, seeking new territories, and mating successfully . Recently, Yokoyoma described how pollutant levels of the insecticide diflubenzuron are enough to affect the embryonic development of the caddisfly, causing thorax and leg abnormalities and reducing their survival rates . These few examples are just an indicator of the effects humans are having on the environment in terms of pollutants from the pharmaceutical and agrochemical industries, but many more studies have been published with similarly concerning results …”

“… 33 Currently, residues of various fluorinated organic compounds (polyfluoroalkyl substances, drugs, and agrochemicals) can be detected in surface waters and biological samples. 33 − 36 The history of various polychlorinated compounds (DDT, γ-hexachlorocyclohexane, polychlorinated biphenyls, etc.) clearly illustrates the dangers of such persistent organic pollutants.…”

“…On the other hand, many fluorinated entities, especially perfluorinated ones, are highly resistant to degradation, leading to their accumulation in the environment . Currently, residues of various fluorinated organic compounds (polyfluoroalkyl substances, drugs, and agrochemicals) can be detected in surface waters and biological samples. − The history of various polychlorinated compounds (DDT, γ-hexachlorocyclohexane, polychlorinated biphenyls, etc.) clearly illustrates the dangers of such persistent organic pollutants …”