Observation of morphological abnormalities in silkworm pupae after feeding 137CsCl-supplemented diet to evaluate the effects of low dose-rate exposure

Abstract

Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, morphological abnormalities in lepidopteran insects, such as shrinkage and/or aberration of wings, have been reported. Butterflies experimentally exposed to radiocesium also show such abnormalities. However, because of a lack of data on absorbed dose and dose–effect relationship, it is unclear whether these abnormalities are caused directly by radiation. We conducted a low dose-rate exposure experiment in silkworms reared from egg to fully developed larvae on a 137CsCl-supplemented artificial diet and estimated the absorbed dose to evaluate morphological abnormalities in pupal wings. We used 137CsCl at 1.3 × 103 Bq/g fresh weight to simulate 137Cs contamination around the FDNPP. Absorbed doses were estimated using a glass rod dosimeter and Monte Carlo particle transport simulation code PHITS. Average external absorbed doses were approximately 0.24 (on diet) and 0.016 mGy/day (near diet); the average internal absorbed dose was approximately 0.82 mGy/day. Pupal wing structure is sensitive to radiation exposure. However, no significant differences were observed in the wing-to-whole body ratio of pupae between the 137CsCl-exposure and control groups. These results suggest that silkworms are insensitive to low dose-rate exposure due to chronic ingestion of high 137Cs at a high concentration.

Imaging Plate Autoradiography for Ingested Anthropogenic Cesium-137 in Butterfly Bodies: Implications for the Biological Impacts of the Fukushima Nuclear Accident

“…These results were in contrast to previous field-based studies. However, these results are consistent with a similar study in Tanaka et al (2020) [ 50 ], in which 137 CsCl was given to silkworms. These key experiments [ 49 , 50 ] have demonstrated that these lepidopteran insects and possibly other insects are resistant against relatively low-dose radioactive exposure itself under experimental conditions in the laboratory despite their vulnerability in the field.…”

“…However, these results are consistent with a similar study in Tanaka et al (2020) [ 50 ], in which 137 CsCl was given to silkworms. These key experiments [ 49 , 50 ] have demonstrated that these lepidopteran insects and possibly other insects are resistant against relatively low-dose radioactive exposure itself under experimental conditions in the laboratory despite their vulnerability in the field. This discrepancy between field-based and laboratory-based results is called the field–laboratory paradox [ 51 ], which led us to propose that the biological effects on the pale grass blue butterfly in Fukushima in the field are mediated by “field effects”, one of which is mediated by ecological interactions with its host plant [ 43 , 44 , 45 , 46 , 51 ].…”

The second decade of the blue butterfly in Fukushima: Untangling the ecological field effects after the Fukushima nuclear accident

“…Later, this interpretation turned out to be incorrect; the pale grass blue butterfly was resistant to high levels of 137 Cs ingestion from an artificial diet (Gurung et al, 2019). High radiation resistance of lepidopteran insects was also confirmed by the silkworm moth in a similar feeding experiment (Tanaka et al, 2020).…”

A Case of Iodine 125 Seeds (I-125) Responding to Lung Squamous Cell Carcinoma

“…8 The absorbed dose rate of internal exposure (0.81 mGy/day) was higher than that of external irradiation (0.21 mGy/day). 9 It has been reported that I-125 seeds was safe and effective in a variety of different tumors, such as head and neck cancer, 10 parotid adenoid cystic carcinoma, 11 high-grade gliomas, 12 papillary thyroid carcinoma recurrence, 13 and even in vulvar squamous cell cancer. 14 In this article, we described a case with LUSC patient who was treated using I-125 seeds in our department in recent years.…”