Takeshi Sakurai

Cultured muscle tissues have been integrated with artificial structures to construct biohybrid robots capable of diverse soft movements. However, most existing designs depend on artificial skeletons, limiting their flexibility and biomimetic potential. In this study, we propose a jointless, tongue‐like bioactuator composed entirely of skeletal muscle tissues. Inspired by the human tongue's multidirectional muscle architecture, vertically and horizontally aligned muscle tissues were assembled orthogonally. By exploiting the anisotropic responsiveness of muscle to directional electrical stimulation, the actuator exhibited distinct multidirectional motion patterns—swinging and lateral compression under horizontal stimulation, and swinging with enhanced linear contraction under vertical stimulation. Motion trajectory analysis confirmed that these multiaxis movements could be precisely controlled by tuning the direction and strength of stimulation. These results demonstrate that the configuration of orthogonally aligned muscle tissues can drive versatile multidirectional motion without rigid frameworks, providing a fully biological and biomimetic approach for achieving complex, multidegree‐of‐freedom actuation in muscle‐based biohybrid systems.

Synopsis: Animals can adaptively behave in different environmental conditions by converting environmental information obtained from their sensory organs into actions. This sensory–motor integration enables the accomplishment of various tasks and is essential for animal survival. This sensory–motor integration also plays an important role in localization to females, relying on sex pheromones floating in space. In this study, we focused on the localization behavior of the adult male silk moth, Bombyx mori. We investigated sensory–motor integration against time delay using odor plume tracking performance as an index when we set a certain time delay for the sensory and motor responses. Given that it is difficult to directly intervene in the sensory and motor functions of the silk moth, we constructed an intervention system based on a mobile behavior measurement system controlled by them. Using this intervention system, not only can timing the detection of the odor in the environment and timing the presentation of the odor to the silk moth be manipulated, but timing the reflection of the movement of the silk moth can also be manipulated. We analyzed the extent to which the localization strategy of the silk moth could tolerate sensory delays by setting a delay to the odor presentation. We also evaluated behavioral compensation by odor sensory feedback by setting a delay to the motor. The results of the localization experiment have shown that the localization success rate did not decrease when there was a motor delay. However, when there was a sensory delay, the success rate decreased depending on the time delay. Analysis of the change in behavior after detection of the odor stimulus has shown that the movement was more linear when we set a motor delay. However, the movement was accompanied by a large rotational movement when there was a delay in the sensory input. This result has suggested that behavior is compensated for the delay in motor function by feedback control of odor sensation, but not when accompanied by sensory delay. To compensate for this, the silk moth may acquire appropriate information from the environment by making large body movements.

近年，生物の嗅覚について分子レベルでの研究が活発に行われており，様々なにおい物質への応答のデータベース化が進んでいる．生物の中でも特に昆虫はにおいの検出能力が優れており，研究対象として遺伝子工学的手法に基づいた嗅覚メカニズムの解明が著しい．そこで，我々は昆虫の嗅覚系に着目し，においセンサへの応用を見据えて昆虫の嗅覚受容体および生体の活用を検討している．本稿では，異種細胞での昆虫嗅覚受容体発現系の利用や遺伝子改変昆虫の作出について解説する．

Male moths are capable of orienting towards conspecific females using sex pheromones. Since pheromones are distributed as discontinuous plumes owing to air turbulence, tracking intermittent stimuli with high temporal resolution is suggested to be important for efficient localisation. Here, using a pheromone binding protein (BmPBP1) knockout silkmoth, we revealed that the loss of functional pheromone binding protein altered antennal response kinetics resulting in reduced temporal resolution to intermittent pheromone stimuli on the antennae. Behavioural analysis revealed that BmPBP1 -knockout males exhibited significantly less straight walking, which occurs when detecting pheromone stimuli, especially to high frequency stimuli. Accordingly, BmPBP1 -knockout males took a significantly longer time to locate pheromone sources and females than did wild-type males. Together, BmPBP1 plays a critical role in determining temporal antennal response kinetics and that an appropriate range of temporal sensory and behavioural resolutions is essential for tracking pheromone plumes for efficient pheromone source localisation in the silkmoth.

In this letter, a system that discriminates between two odorants in real-time with a single antenna of an insect was constructed. In previous studies, odorants were discriminated through arraying multiple types of sensors. However, the use of a sensor array enlarges the entire system and requires complex signal processing, which makes it difficult to mount the system on a quadcopter with limited payloads or an autonomous robot with low computational power. On the other hand, the antenna of an insect is composed of several olfactory receptors; thus, a single antenna responds to multiple odorants. Therefore, a system for discriminating between multiple odorants from the electroantennogram (EAG) signal of a single antenna of an insect is proposed. An antenna of an adult male silkmoth is employed; the silkmoth antenna exhibits an electric potential change when detecting an odor, but the difference in the EAG amplitude and recovery time depends on the type of odorant. Since EAG is a type of neural signal, it is difficult to perform odor discrimination by simply setting the threshold, because it drifts due to noise. Therefore, the Hodgkin-Huxley model (HH model) was applied to the raw EAG signal as a dynamic filter, and the spike firing rate of the output value was calculated using the HH model. Then, the odorants were discriminated against based on the magnitude of the spike firing rate. A series of signal processing was implemented in a microcontroller, and the experiments indicated that all antennae demonstrated a discrimination performance of 90$\%$ or more.