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Newly hatched phyllosomas of Thenus orientalis (Lund) were successfully reared under conditions of natural light (D/L), continuous dark (24D) or continuous light (24L). Survival, duration of intermoult periods, moult increment in total body length, and timing of moulting through larval stages were monitored. Survival and growth under 24L was lower than that under D/L and 24D; this may be a result of decreased phyllosomal feeding activity under 24L, caused by a photopositive reaction drawing the phyllosomas away from food at the bottom. There were no differences in phyllosomal development under D/L and 24D. When phyllosomas were reared under D/L, moulting was synchronized and occurred around dawn. Moulting of those reared under 24D or 24L was not synchronized and occurred irregularly. These results indicate that, in phyllosomas, light regime influences the endogenous rhythmic function responsible for the regulation of moulting time. When phyllosomas reared under D/L metamorphosed to the nisto stage, synchronized moulting switched from dawn to after dusk. Furthermore, nistos and juveniles moulted only nocturnally, with apparent synchronicity. This suggests that the switch from planktonic to benthic lifestyle, with consequent different predation pressures, necessitates a change in the timing of moulting.

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Massive environmental monitoring has been conducted continuously since the Fukushima Daiichi Nuclear Power accident in March of 2011 by different monitoring methods that have different features together with migration studies of radiocesium in diverse environments. These results have clarified the characteristics of radiological environments and their temporal change around the Fukushima site. At three months after the accident, multiple radionuclides including radiostrontium and plutonium were detected in many locations; and it was confirmed that radiocesium was most important from the viewpoint of long-term exposure. Radiation levels around the Fukushima site have decreased greatly over time. The decreasing trend was found to change variously according to local conditions. The air dose rates in environments related to human living have decreased faster than expected from radioactive decay by a factor of 2-3 on average; those in pure forest have decreased more closely to physical decay. The main causes of air dose rate reduction were judged to be radioactive decay, movement of radiocesium in vertical and horizontal directions, and decontamination. Land-use categories and human activities have significantly affected the reduction tendency. Difference in the air dose rate reduction trends can be explained qualitatively according to the knowledge obtained in radiocesium migration studies; whereas, the quantitative explanation for individual sites is an important future challenge. The ecological half-lives of air dose rates have been evaluated by several researchers, and a short-term half-life within 1 year was commonly observed in the studies. An empirical model for predicting air dose rate distribution was developed based on statistical analysis of an extensive car-borne survey dataset, which enabled the prediction with confidence intervals. Different types of contamination maps were integrated to better quantify the spatial data. The obtained data were used for extended studies such as for identifying the main reactor that caused the contamination of arbitrary regions and developing standard procedures for environmental measurement and sampling. Annual external exposure doses for residents who intended to return to their homes were estimated as within a few millisieverts. Different forms of environmental data and knowledge have been provided for wide spectrum of people. Diverse aspects of lessons learned from the Fukushima accident, including practical ones, must be passed on to future generations.