Akihiro Miyanoshita

Age- and time interval-specific gamma radiation-induced DNA damage in adult maize weevils, Sitophilus zeamais Motschulsky, assessed using comet assays

The gamma radiation-induced DNA damage in adult maize weevils, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), was assessed using single-cell electrophoresis (comet assay). Analysis of DNA damage following 0.5 and 1.0 kGy of gamma radiation was performed using cells from 1- and 15-day-old adults. Gamma-irradiated adults from both age groups showed typical DNA fragmentation, whereas cells from non-irradiated adults showed more intact DNA than young S. zeamais. Investigations using the comet assay showed that tail length, % tail DNA and % DNA damage all increased in adults of both age groups when compared to the control insects. A maximum comet length of 227.33 μm was recorded for 15-day-old adults at 24h after irradiation with 1.0 kGy and a minimum of 50.12 μm for 1-day-old adults at 0 h after irradiation with 0.5 kGy. The percentage of DNA damage increased up to 57.31% and 68.15% for 1- and 15-day-old adults, respectively, at 24h after irradiation with 1.0 kGy, whereas only 8.58% and 12.22% DNA damage were observed in the control batches. The results also showed that percentage of DNA damage increased at 24h after irradiation compared to that at 0 h. However, further studies are needed to confirm these results.

Infestation and Development of Sitophilus spp. in Pouch-Packaged Spaghetti in Japan

Abstract Infestation of pouch-packaged spaghetti by Sitophilus oryzae (L.) (Coleoptera: Curculionidae) was observed in Japan in May 2006. It was suggested that 30% of all shipped pasta products sustain damage to the packages heat-sealed before reaching retail stores. Hence, we investigated the mechanisms by which S. oryzae and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults invade pasta packaged in polypropylene pouches. In the damaged packages, both species entered through the breaks in the seal and laid their eggs on the pasta. However, in the intact packages, the adults of both species bit around air vent holes in the film, but they did not make the holes big enough for entry into the pouch. We also compared each species’ developmental periods from oviposition to emergence in pasta and brown rice (Oryza spp.). The average developmental period of both species at 25°C was shorter in rice than in pasta. The number of individuals emerging from brown rice was significantly higher than that from pasta. Finally, we suggested a measure to prevent infestation by insect pests in pouch-packaged pasta products.