Infrared Vertical Cavity Surface-Emitting Laser barriers to measure movements of freshwater and marine invertebrates

In this article, we present an optical system based on Infrared VCSEL Laser and NPN phototransistor. The output signal of each optoelectronic emitter-receiver couple is managed by a cheap electronic circuit, which ensures high flexibility and the modularity of the various components of the system. At the end of the measurement chain, there is the Raspberry-Pi model 3B+. The aim of the current work was to design a system able to monitor locomotor activity of small marine and freshwater animals: nudibranch Melibe viridis and cave decapod Typhlocaris salentina. Our results showed that the optical system can detect the movement of small aquatic animals inside medium and big aquaria. From an ethological point of view, these results show that the device can be useful for monitoring the locomotor activity, including long-term monitoring needed to characterize the chronobiological parameters of these animals. In conclusion, we have found the IR-actuated movement detector to be a highly sensitive and reliable device, in spite of its relatively low cost. It is appropriate to a wide range of experiment protocols and data-recording systems.