Akira Hirano

Unconstrained and noninvasive measurement of bioelectric signals from small fish

Recently, the technique of fish bioassay has attracted attention as a method for constant monitoring of aquatic contamination. The respiratory rhythms of fish are considered to be an efficient indicator for the monitoring of water quality, since they are sensitive to chemicals and can be measured indirectly from the bioelectric signals generated by their breathing. However, no method has yet been established to measure signals in small free-swimming fish. In this article, we propose a system to measure bioelectric signals in small fish and monitor the frequency component in real time. To cover the large measurement range required in a free-swimming environment, the signals are measured using multiple electrodes. Further, the system focuses on the frequency component of the signal to assess the condition of the fish using frequency analysis and a band-pass filter. Experiments were conducted with the purpose of enabling remote sensing and environment estimation. First, it was verified that the measured signals were synchronized with the breathing of the fish. Then, a remote sensing experiment was performed using medaka (Oryzias latipes) that were allowed to swim freely in a measurement aquarium. The results confirmed that bioelectric signals which were synchronized with breathing could be measured in unconstrained and noninvasive conditions.

An electrophysiological model of chemotactic response in Paramecium

In order to survive in complex natural environments, living organisms have been genetically acquiring various algorithms. Paramecium, for example, exhibits an avoiding reaction when it senses repellent chemicals on the anterior part of the cell. Also, on sensing attractants, it accelerates its swimming velocity and remains in the area. Such a chemotactic response is called chemotaxis. In this paper, we proposes the computer model of Paramecium based on biological knowledge. And, we report the simulation experiments that the computer model can reproduce the characteristics of the actual organism.

Bioassay System Based on Behavioral Analysis and Bioelectric Ventilatory Signals of a Small Fish

Particular attention has recently been paid to bioassay systems that allow the responses of living organisms to be monitored to support water quality evaluation. This technology can complement traditional chemical inspection methods, which have limitations in terms of chemical substance coverage and inspection frequency. This paper proposes a bioassay system that can be used to detect the water contamination by monitoring the behavior and ventilatory signals of zebrafish. Rather than engaging an optical device, the system extracts behavioral information from the ventilatory signals measured via an electrode array, thereby providing advantages in terms of robustness against changes in environmental light. This paper then describes the capacity of the proposed system to detect contamination with ethanol (a low-toxicity substance) as an example.

Biomimetic Control of Mobile Robots Based on the Chemotactic Response Model of Paramecium

In order to survive in complex natural environments, living organisms have been genetically acquiring various algorithms. Recently, the concept of Software Biology has been propoed, in which the algorithms of living organisms are considered as a kind of software that could be utilized for robot control. We have proposed the computer model of Paramecium, Virtual Paramecium, based on biological knowledge. Virtual Paramecium can approximately realize the chemotatic behavior of actual Paramecium. In this paper, we report the results obtained when a mobile robot is controlled using Virtual Paramecium, and confirm the effectiveness of the biomimetic control based on the information processing algorithm of living organisms.