Effects of Radiation From Contaminated Soil and Moss in Fukushima on Embryogenesis and Egg Hatching of the Aphid Prociphilus oriens.

Radiation-contaminated soils are widespread around the Fukushima Daiichi Nuclear Power Plant, and such soils raise concerns over its harmful effect on soil-dwelling organisms. We evaluated the effects of contaminated soil and moss sampled in Fukushima on the embryogenesis and hatching of aphid eggs, along with the measurement of the egg exposure dose. Cs-137 concentration in soil and moss from Fukushima ranged from 2200 to 3300 Bq/g and from 64 to 105 Bq/g, respectively. Eggs of the eriosomatine aphid Prociphilus oriens that were collected from a non-contaminated area were directly placed on the soil and moss for 4 or 3 months during diapause and then incubated until hatching. The total exposure dose to the eggs was estimated as ca. 100-200 mGy in the 4-month soil experiment and 4-10 mGy in the 4-month moss experiment. There was no significant difference in egg hatchability between the contaminated soil treatment and the control. No morphological abnormalities were detected in the first instars that hatched from the contaminated soil treatment. However, we found weak effects of radiation on egg hatching; eggs placed on the contaminated moss hatched earlier than did the control eggs. On the contaminated soil, the effects of radiation on egg hatching were not obvious because of uncontrolled environmental differences among containers. The effects of radiation on egg hatching were detected only in containers where high hatchability was recorded. Through the experiments, we concluded that the aphid eggs responded to ultra-low-dose radiation by advancing embryogenesis.