When threatened by the giant hornet Vespa mandarinia Smith (Hymenoptera: Vespidae), the Japanese honey bee Apis cerana japonica Radoszkowski (Hymenoptera: Apidae) collects substances from the surrounding environment and applies them to the entrance of its hive. This behavior is thought to help avoid mass attacks by hornets. To investigate the substances collected by the bees, we analyzed the DNA extracted from the applied spots using three methods. First, we placed glass slides at the hive entrance, extracted DNA from the spots mounted on the glass slides, and amplified the internal transcribed spacer (ITS) 1 using PCR. Sequencing of the cloned PCR products revealed the presence of both plant and fungal DNA. Second, we performed an amplicon analysis targeting ITS2 of plants and fungi using next-generation sequencing. A diverse array of fungi was detected; however, unexpectedly, no plant DNA was detected. The reason for this remains unclear; however, amplicon analysis appears to be biased toward the detection of fungi. Therefore, in the third experiment, we extracted DNA from individual spots on glass slides, amplified ITS1, and directly sequenced the PCR products. This experiment allowed us to quantify the utilization of plants and fungi based on the number of spots containing each type of material. We determined the sequences of 165 PCR products, including 56 obtained from plants, 68 from mushrooms, and 41 from non-mushroom fungi.

The behavioral physiology of males in social wasps has received little attention, despite the importance of male behavior adapted to complex social environments. To explore the roles of brain biogenic amines in mating-related behavior in male Japanese yellow hornets (Vespa simillima), we first determined the development of mating-related behavior and age-related changes to biogenic amines in the brain. The activities of locomotion, flight, and mating in the males increased with day-age by 1 week after emergence. Testes size decreased within 1 week after adult emergence, suggesting that male sexual maturation may be complete with the development of mating-related behavior. Serotonin levels in the brain increased with age in parallel to the behavioral activities. Dopamine levels in the brain peaked at 2 days of age and then decreased with age, whereas octopamine levels in the brain decreased with age. Thus, serotonin was a candidate compound activating mating-related behavior in males. We then examined the effects of serotonin on the mating-related behavior of males using serotonin injections. Injections of serotonin significantly enhanced activities of locomotion, flight, and mating, depending on serotonin concentration. Those results suggested that serotonin activates mating-related behavior in male hornets.

External sources of neutron provide stable and sufficient neutron for initial startup of a nuclear reactor. They also provide signals for neutron detectors to monitor the safety of reactor during shutdown. In the high temperature engineering test reactor (HTTR), Cf-252 is used as the external neutron source. However, the Cf-252 sources must be renewed every approximately 7 years because of its relatively short half-life of 2.6 years. The renewal of Cf-252 sources requires a high cost and a very complicated procedure. This study investigated the feasibility of using BeO rods as the secondary neutron sources to avoid renewing the Cf-252 neutron sources periodically. The BeO rods could exist in the reactor for a long time so that if the reactor operates long enough, the neutron flux at the wide-range monitoring detectors remains more than 10n.s(-1).cm(-2) even if the reactor is shutdown for as long as 5 years. The results of this study indicated that using BeO rods as the secondary neutron sources would be an attractive option for the future HTGR design with a long-life fuel cycle.

The rapid naturalization of Bombus terrestris across the Nemuro Peninsula has led to a decline in two closely related native Japanese species, namely Bombus hypocrita sapporensis and Bombus cryptarum florilegus, both belonging to the common subgenus Bombus. Although it is widely believed that cross-mating of native and non-native species is influenced by the common male sex pheromone in this region, no study has been conducted to substantiate this claim. Thus, we investigated the cross-activities of male sex pheromones between native and non-native bumblebees, as well as the frequencies of cross-mating, using chemical and DNA assays. Our gas chromatography-electroantennographic detector analyses and behavioral tests revealed the presence of sex pheromonal cross-activities between B. terrestris and the two Japanese bumblebees species. Furthermore, DNA analyses revealed the occurrence of cross-mating between native and non-native species in the Nemuro Peninsula. Overall, these results indicate the immediate need for conservation measures to safeguard Japanese bumblebee populations in the Nemuro Peninsula.

Bombus cryptarum florilegus is a rare bumblebee in Japan. We tried to rear this bumblebee under laboratory conditions to investigate its nesting habits and colony development. Five queens out of 15 were successful in establishing colonies, and new queens and males were produced from these colonies. In the laboratory colonies, the average numbers of workers, males, and new queens per colony of B. cryptarum florilegus were 15.2 ± 4.7, 26.0 ± 8.0, and 2.0 ± 2.1, respectively. Although a feral colony producing five hundred cocoons has been reported, B. cryptarum florilegus established small colonies under laboratory conditions. Further study suggests that the improvement of rearing technique is required to produce the large colony of B. cryptarum florilegus.

Estimation of decay gamma distribution in a reactor core is essential for safely conducting various works after reactor shutdown such as periodic maintenance, shuffling fuel, removing spent fuel at the end of cycle, etc. Because of the dependency on the complex operating history of the reactor, attempting to calculate the decay gamma rays distribution in the core remains a challenge. This study shows a method to calculate the shutdown gamma distribution in the HTTR core by coupling a Monte-Carlo transport calculation code MCNP6 and an activation code ORIGEN2 to take advantage of spatial dependence and transport abilities of MCNP6 and the detailed fission products tracking during burnup and cooling of ORIGEN2. As result, the three-dimensional shutdown gamma distribution in the HTTR core for different cooling times and spatial locations could be obtained accurately.

Some aphid species produce a soldier caste with enlarged forelegs and horns (weapons). It has been hypothesised that the evolution of morphological specialization by soldiers in social aphids is accelerated by high predation pressure, but this possibility has not been tested. Here, we investigated the relationship between local predator abundance and soldiers’ weapon size and aggressiveness in a prey–predator system comprising a eusocial aphid, Ceratovacuna japonica , and its predators (larvae of the butterfly Taraka hamada and of the moth Atkinsonia ignipicta ) in two populations with different predator abundances. We found that the soldiers in the predator-abundant population had larger weapons and were more aggressive than those in the population with lower predator abundance. Furthermore, the soldiers’ defensive prowess (evaluated as the survival of aphids in the presence of predators) was greater in the predator-abundant population. These results provide the first evidence that a population of eusocial aphids experiencing high predation pressure has soldiers with pronounced defensive traits and defensive prowess.

Abstract Background The Japanese honeybee, Apis cerana japonica, shows a specific defensive behavior, known as a “hot defensive bee ball,” used against the giant hornet, Vespa mandarinia. Hundreds of honeybee workers surround a hornet and make a “bee ball” during this behavior. They maintain the ball for around 30 min, and its core temperature can reach 46. Although various studies have been conducted on the characteristics of this behavior, its molecular mechanism has yet to be elucidated. Here, we performed a comprehensive transcriptomic analysis to detect candidate genes related to balling behavior. Results The expression levels of differentially expressed genes (DEGs) in the brain, flight muscle, and fat body were evaluated during ball formation and incubation at 46 °C. The DEGs detected during ball formation, but not in response to heat, were considered important for ball formation. The expression of genes related to rhodopsin signaling were increased in all tissues during ball formation. DEGs detected in one or two tissues during ball formation were also identified. Conclusions Given that rhodopsin is involved in temperature sensing in Drosophila, the rhodopsin-related DEGs in A. cerana japonica may be involved in temperature sensing specifically during ball formation.

In the late 1980s, the seismic classification of the high temperature engineering test reactor (HTTR) was formulated during its design stage. Because of the HTTR's lack of operation experiences to sufficiently under -stand the safety characteristics of high temperature gas cooled reactors (HTGRs) at that time, the seismic clas-sification of commercial light water reactors (LWRs) was applied to HTTR. However, subsequent operation experiences and test results using HTTR made it clear that the seismic classification of commercial LWRs was somewhat too conservative for the HTGRs. The seismic classification of HTTR was reevaluated using the following approach. Class S facilities with high safety requirements ensured that they maintained their function even when the safety functions of Class B and Class C facilities were lost during earthquake-triggered accidents, thereby safely controlling the accident without exposing the members of the public in the vicinity of the reactor to excessive radiation exposure. Consequently, Class S facilities were downgraded compared with the com-mercial LWRs. Moreover, an evaluation was conducted to verify the validity of the new seismic classification under the conditions where the functions of Class B and Class C facilities are lost. It was confirmed that the reactor was stable and that the evaluated public dose was below the authorized limit. In June 2020, the Nuclear Regulatory Authority in Japan confirmed that the results of the seismic classification conformed to the standard rules of the reactor installation change.

Intercolony drifting of the Japanese paper wasp, Polistes rothneyi Cameron, was observed using individual color marking of workers. No genetic relatedness was found by using microsatellite markers between drifting workers and the recipient colony. Genetic analysis of brood in the recipient colony revealed reproduction by non-kin drifting worker(s) in the queenless host colony. The non-kin broods were raised like broods of the recipient colony until the genetic analysis. This study is the first evidence of male production by non-kin workers in temperate eusocial wasps. This natural event would compensate for fitness loss as an alternative reproductive strategy evolved under predation and climatic pressures, and is also discussed from the viewpoint of mutual help.

The following design details of the high temperature engineering test reactor (HTTR) are described: nuclear, thermal-hydraulic seismic and safety performance, metal and graphite components, core components and reactor internals, and cooling, reactivity control, instrumentation and control systems. The new design criteria have been developed for graphite structures, and a super heat-resistant alloy, Hastelloy XR, was newly developed for high temperature components such as heat transfer tubes of an intermediate heat exchanger. The performance and structural integrity of the fuel core components and reactor internals were verified in advance by the research and development described in Chapter 3, R&D on Components. As for the safety design, the strategy of defense in depth was implemented so that the safety engineering functions such as control of reactivity, removal of residual heat, and confinement of fission products shall be well performed to ensure safety.

Integrity confirmation for buildings against collisions of projectiles has been conducted to evaluate their behavior upon collision between a projectile with a simple shape and a wall using empirical formulas. However, there is a possibility that structures with a complex shape such as a stack may collide with a reactor building. However, there have been few studies of collisions between structures with a complex shape and buildings. In this study, it is necessary to set the physical properties of reinforced concrete to carry out such an evaluation; however, the physical properties depend on the number of reinforcing bars. For this reason, the physical properties of reinforced concrete are set so as to fit conventional empirical formulas recommended. Impact evaluation was carried out using a reactor building and a stack with a realistic shape and physical properties.

Honey bees and bumble bees belong to the same family (Apidae) and their workers exhibit a division of labor, but the style of division of labor differs between species. The molecular and neural bases of the species-specific social behaviors of Apidae workers have not been analyzed. Here, we focused on two immediate early genes, hormone receptor 38 ( HR38 ) and early growth response gene-1 ( Egr1 ), and late-upregulated ecdysone receptor ( EcR ), all of which are upregulated by foraging flight and expressed preferentially in the small-type Kenyon cells of the mushroom bodies (MBs) in the honey bee brain. Gene expression analyses in Bombus ignitus revealed that HR38 and Egr1 , but not EcR , exhibited an immediate early response during awakening from CO 2 anesthesia. Both premature mRNA for HR38 and mature mRNA for Egr1 were induced during foraging flight, and mRNAs for HR38 and Egr1 were sparsely detected inside the whole MB calyces. In contrast, EcR expression was higher in forager brains than in nurse bees and was expressed preferentially in the small-type Kenyon cells inside the MBs. Our findings suggest that Kenyon cells are active during foraging flight and that the function of late-upregulated EcR in the brain is conserved among these Apidae species.

Previous reports note that males of the Japanese bumblebee Bombus ardens ardens perform nest surveillance to mate with new queens. Here, we report that males of this species also perform patrolling and scent-marking for mating. We observed that many B. ardens ardens males fly together from May to June in circular paths through a wooded area in Tokyo, Japan. The flight activity is bimodal with peaks in the morning and late afternoon. When tethered new queens were presented at a focal point, males approached, touched, or grabbed them but ignored them at a foraging site. Males performed scent-marking on tree leaves only in the early morning (05:30 to 07:30), and compounds from the labial gland of B. ardens ardens males were detected on a scent-marked leaf. Based on these findings and previous reports, we conclude that males of this species have at least two mating tactics or strategies: nest surveillance and patrolling.

Gynandromorphy, which is characterized by the coexistence of male and female tissues in a single individual, is known in insects. Gynandromorphs exhibit diverse levels of defects in sexual behavior. The distribution pattern of both sexes within the nervous systems could be responsible for these differences in behavioral traits; however, most studies have mainly focused on the unique external morphological traits of gynandromorphs, and little attention has been paid to the evaluation of nervous systems, at least in Hymenoptera. In this study, we evaluated a gynandromorphic individual of bumblebee (Bombus ignitus) with a bilaterally dimorphic head and thorax (left side, male; right side, female) and a uniformly masculine gaster. The gynandromorph exhibited abnormal sexual behavior; it normally approached and touched virgin queens but rarely made subsequent copulation attempt. Dissection of the gaster indicated that it possessed a set of male reproductive organs. We analyzed the encephalic and antennal expression patterns of the fruitless (fru) gene, which shows sex-specific alternative splicing conserved in various insect orders and has been thought to act as the master regulator of sexual behavior in male nervous systems. The gynandromorph showed left-side-biased expression of male-type fru transcripts. We discuss a possible mechanism for the observed unusual interruption of sexual behavior of the gynandromorph by reference to the fru expression pattern and our recent findings on the sexually dimorphic response to female-derived pheromones.

Lone Bombus ignitus queens are known to start nests in small underground cavities. To examine the nest‐site preference of post‐hibernating queens, choice tests were carried out by providing queens with orphan colonies and empty cavities as possible nesting sites within an experimental box. Our results showed that the queens had a strong preference for takeover of an orphan colony, suggesting that nest takeover (usurpation) could occur in nature even with the presence of possible empty cavities for nesting. We compared the colony‐growth process and final production of sexuals between non‐takeover and takeover colonies. The increase in the number of egg cups was faster in the takeover colonies, suggesting that orphan broods elicit earlier oviposition by the usurping queen. Reproductives emerged earlier (significant for new queens) and in greater numbers (males) from takeover colonies than from non‐takeover colonies. Thus, post‐hibernating B. ignitus queens would search for and take over small orphan colonies to increase their fitness.

In the present study, ICP-MS with a new hybrid simultaneous preconcentration combining solid phase extraction using chelating resin and iron hydroxide coprecipitation in one batch at a single pH adjustment (pH 6.0) were developed for multielement determination of trace metal ions in seawater. In multielement determination, the present method makes it possible to determine Cr(III), As(V), Se (IV), and other 14 trace metal elements (Ti, V, Co, Ni, Cu, Zn, Zr, Ge, Cd, Sb, Sn, W, Pb, and U) in seawater. Moreover, for speciation analyses of Cr, As, and Se, the pH dependence on recovery for the different chemical forms of Cr, As, and Se was investigated. In speciation analyses, Cr, As, and Se were determined as the total of Cr (III) and a part of Cr (VI), total of As (III) and As (V), and Se(IV), respectively. Determination of total of Se and Cr(VI) remains as future task to improve. Nevertheless, the presentmethod would have possibility to develop as the analytical method to determine comprehensivelymostmetal elements in all standard and guideline values in quality standard in environmental water in Japan, that is, most toxic metal elements in environmental water.

Asian honeybees (Apis cerana) have evolved a thermal collective defense against the sympatric giant hornet (Vespa mandarinia) in which workers surround the predator en masse and produce heat up to 46 °C to kill it. This characteristic behavior is called “hot defensive bee ball formation.” Many studies have described the uniqueness and efficiency of this behavior; however, little attention has been paid to the potential cost to the honeybee. In this study, we focused on potential effects to bee ball-participating honeybees. We compared life expectancy of same-age ball-participating honeybees and nonparticipating honeybees and demonstrated that the life expectancy of the bee ball-participating honeybees was dramatically shortened. The 46 °C exposure also shortened the life expectancy of honeybees with induced expression of the heat shock protein gene, strongly implicating the increased temperature inside the bee ball in the deleterious effect on participating honeybees. We additionally found that bee ball-participating and then short-lived worker honeybees had a tendency to join a subsequent bee ball more aggressively. This tendency could mitigate accumulation of the short-lived worker honeybees within the colony, which otherwise would cause a severe reduction of honeybee colony activity.