Detection of DNA damage in larvae and adults of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) exposed to hypoxia at different temperatures using the comet assay

Abstract

The red flour beetle, Tribolium castaneum is considered one of the most important pests of grains and stored products. Its adults and larvae feed on flour, grain germ and endosperm, and contaminate grains and stored products with their body parts and feces. In heavy infestation, the products become unusable for human consumption. So this study aimed to evaluate the effect of hypoxia (using non-toxic gases) on flour beetle larvae and adults under temperatures of 15, 25 and 35 °C using 97 and 98% nitrogen at several exposure periods. Also, DNA damage was measured in untreated and treated insects with LT₅₀ of 98% N₂ at different temperatures by comet assay. The results showed that, at 97 and 98% N₂, the complete adult mortality was achieved after 17 & 13 days at 15 °C, which decreased to 9 & 8 days at 25 °C and 7 & 6 days at 35 °C. While the larvae treated with nitrogen at 15, 25 and 35 °C needed exposure periods of 13, 9 and 4 days at 97% N₂ and 12, 7 and 3 days at 98% N₂ to achieve complete mortality. The comet assay showed that, DNA in adults and larvae was damaged at different levels according to temperatures; the tail length increased from 5.95 to 8.82 μm and DNA in tail was 10.52% increased to 12.86% when temperature increased from 15 °C to 35 °C. The tail length of treated larvae was 6.41μm increased to 7.66 μm and the DNA in tail was 9.51% increased to 11.59% when temperature increased from 25 to 35 °C. In conclusion, the results showed significant damage to the DNA of larvae and adults treated with the highest concentration and temperature used, so we recommend treating adults and larvae of T. castaneum with 98% N₂ for 6 days at 35 °C to control this pest.