Terrestrial isopods congregate under a low-level beta-emitter source
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Updated: Sep 29, 2026

Collecting Marine Gnathiid Isopod Fish Parasites with Light Traps
Published on: September 25, 2023
Tomoko Kanao1, Yukihisa Miyachi, Takeshi Yamada
1Department of Radiological Sciences, International University of Health and Welfare, Ohtawara-shi, Tochigi-ken, Japan.
Abstract:
Ionizing radiation is ubiquitous, but very few experiments have investigated the biological effects of the natural background radiation at very low doses (>10 mGy/yr). We examined whether the background radiation, or radiation of a slightly higher level, has a role in evoking changes in behaviors of terrestrial isopods (woodlice). Upon exposure to a source giving 15 times the background level placed at one end of a box, a significant increase in the number of woodlice gathering under the beta-source was observed with time, as compared with the sham control. Terrestrial isopods have chemoreceptors (the olfactory system) on the terminal segment of their antennae. An additional experiment confirmed the involvement of these antennae in the radiation effect on behavior. After the excision of the antennae, no beta-taxis response was observed. The behavior of the group exposed to the source giving 30 times the background tended to decrease gradually in the area of the source, and the individuals aggregated in the area away from the source. Thus, the olfactory sensor in the antennae may be an important organ involved in the prompt response to radiation exposure, and the discrimination of the radiation field strengths of radioisotopes.
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