A Distinct Role of the Queen in Coordinated Workload and Soil Distribution in Eusocial Naked Mole-Rats

We investigated how group members achieve collective decision-making, by considering individual intrinsic behavioural rules and behavioural mechanisms for maintaining social integration. Using a simulated burrow environment, we investigated the behavioural rules of coordinated workload for soil distribution in a eusocial mammal, the naked mole-rat (Heterocephalus glaber). We tested two predictions regarding a distinct role of the queen, a socially dominant individual in the caste system: the presence of a queen would increase the workload of other caste individuals, and the cues by a queen would affect the soil distribution. In experiment 1, we placed four individuals of various castes from the same colony into an experimental burrow. Workers exhibited the highest frequency of workload compared to other castes. The presence of a queen activated the workload by other individuals. Individuals showed a consistent workload in a particular direction so as to bias the soil distribution. These results suggest that individuals have a consensus on soil distribution and that the queen plays a distinct role. In experiment 2, we placed the odour of a queen in one of four cells and observed its effect on other individuals’ workload and soil distribution. Relative to other cells, individuals frequently dug in the queen cell so the amount of soil in the queen cell decreased. These results suggest that queen odour is an important cue in coordinated workload and soil distribution in this species

Isotope effects on transport in LHD

Isotope effects are one of the most important issues for predicting future reactor operations. Large helical device (LHD) is the presently working largest stellarator/helical device using super conducting helical coils. In LHD, deuterium experiments started in 2017. Extensive studies regarding isotope effects on transport have been carried out. In this paper, the results of isotope effect studies in LHD are reported. The systematic studies were performed adjusting operational parameters and nondimensional parameters. In L mode like normal confinement plasma, where internal and edge transport barriers are not formed, the scaling of global energy confinement time (τE) with operational parameters shows positive mass dependence (M0.27; where M is effective ion mass) in electron cyclotron heating plasma and no mass dependence (M0.0) in neutral beam injection heating plasma. The non-negative ion mass dependence is anti-gyro-Bohm scaling. The role of the turbulence in isotope effects was also found by turbulence measurements and gyrokinetic simulation. Better accessibility to electron and ion internal transport barrier (ITB) plasma is found in deuterium (D) plasma than in hydrogen (H). Gyro kinetic non-linear simulation shows reduced ion heat flux due to the larger generation of zonal flow in deuterium plasma. Peaked carbon density profile plays a prominent role in reducing ion energy transport in ITB plasma. This is evident only in plasma with deuterium ions. New findings on the mixing and non-mixing states of D and H particle transports are reported. In the mixing state, ion particle diffusivities are higher than electron particle diffusivities and D and H ion density profiles are almost identical. In the non-mixing state, ion particle diffusivity is much lower than electron diffusivity. Deuterium and hydrogen ion profiles are clearly different. Different turbulence structures were found in the mixing and non-mixing states suggesting different turbulence modes play a role

A Distinct Role of the Queen in Coordinated Workload and Soil Distribution in Eusocial Naked Mole-Rats

<div><p>We investigated how group members achieve collective decision-making, by considering individual intrinsic behavioural rules and behavioural mechanisms for maintaining social integration. Using a simulated burrow environment, we investigated the behavioural rules of coordinated workload for soil distribution in a eusocial mammal, the naked mole-rat (<em>Heterocephalus glaber</em>). We tested two predictions regarding a distinct role of the queen, a socially dominant individual in the caste system: the presence of a queen would increase the workload of other caste individuals, and the cues by a queen would affect the soil distribution. In experiment 1, we placed four individuals of various castes from the same colony into an experimental burrow. Workers exhibited the highest frequency of workload compared to other castes. The presence of a queen activated the workload by other individuals. Individuals showed a consistent workload in a particular direction so as to bias the soil distribution. These results suggest that individuals have a consensus on soil distribution and that the queen plays a distinct role. In experiment 2, we placed the odour of a queen in one of four cells and observed its effect on other individuals’ workload and soil distribution. Relative to other cells, individuals frequently dug in the queen cell so the amount of soil in the queen cell decreased. These results suggest that queen odour is an important cue in coordinated workload and soil distribution in this species.</p> </div

The number of experiments for each pattern of composition.

<p>Three colonies (I, II, III) are separately shown.</p

The total frequency of (a) sweeping and (b) digging behaviours during a 90 minute experiment.

<p>Results shown are for each caste in different experimental settings (Q: a queen, n = 3; RM: reproductive males, <i>n</i> = 5; and W: workers, <i>n</i> = 23). Asterisk indicates a significant difference. Individual mean ±1 S.E. is shown.</p

Experimental setup.

<p>Four cells were connected by tunnels in a circle. In total, 300 ‘soil’ particles of different colours were placed in each cell at the beginning of the experiment.</p

The total frequency of (<i>a</i>) sweeping and (<i>b</i>) digging behaviours during a 90 minute experiment.

<p>Results shown are for each caste (RM: reproductive males and W: workers) in different experimental settings. Q(–): experiment 1 without a queen (RM: <i>n = </i>5; W: <i>n</i> = 21); Q(+): experiment 1 with a queen (RM: <i>n</i> = 5; W: <i>n</i> = 23); exp 2: experiment 2 (RM: <i>n</i> = 5; W: <i>n</i> = 16). Asterisk indicates a significant difference. Individual mean ±1 S.E. is shown.</p

Relationships between workload and the type of workload (consensus building or opposite).

<p>Results given are by each caste category (black circles: queen; grey circles: reproductive males; white circles: workers) in experiments 1 and 2. (a, b) In experiment 1, the proportion of consensus building (a: removing soils from the emptied cell vs. its opposite; b: carrying soils into a filled cell vs. its opposite) of the total frequency of sweeping behaviour is shown (number of individuals: queen, n = 3; reproductive males, n = 5; and workers, n = 23). In experiment 2, the proportion of consensus building (removing soils from a queen cell vs. its opposite; number of individuals: reproductive males, n = 5; and workers, n = 16). (c) The frequency of digging in each cell. In experiment 1, the number on the x-axis indicates the order of cells according to the number of soils after the experiments (1 indicates a cell with the least number of soils, and 4 denotes a cell with the largest number of soils). In experiment 2, ‘queen’ and ‘other’ indicate a cell with the queen odour and other cells, respectively. Asterisk indicates a significant difference (p<0.05). Individual mean ±1 S.E. is shown.</p

Illustrated explanation of our definition of “consensus” and “opposite” sweeping.

<p>(a) emptying <i>vs</i>. filling an emptied cell; (b) emptying <i>vs.</i> filling a filled cell.</p