Open-Source Thermometer, Temperature Controller, and Light Meter for Use in Animal Facilities and During Experiments

Experiments with biological samples require precise control of environmental conditions. In our work we use zebrafish ( Danio rerio ) to understand the neurobiology of sleep, which requires precise control of temperature and lighting. Like many labs, lighting and temperature in the animal facility are centrally controlled in the building. During behavioral experiments and microscopy sessions, we use custom-built heating systems and perform occasional manual checks of conditions. However, without a system to precisely record conditions, gradual changes in temperature can go unnoticed for a long time, and temporary failures may be missed entirely. Here we present the design and characterization of affordable open-source tools to record temperature and light conditions during animal experiments using an Arduino microcontroller or a Raspberry Pi compact computer. The waterproof temperature sensor has high stability over 50 days of recording and is precise to 0.1°C. The Arduino device can be used through a common serial port interface for which we present code in Python and MATLAB. The Raspberry Pi version can be accessed through a web interface, for which we provide an installation guide. We use the device to record and review temperature and lighting conditions in two zebrafish animal facilities. We use our platform to add a water heating system to maintain temperature at 28°C during in vivo light-sheet imaging of larval zebrafish. We show that a change in temperature from 28°C to 32°C affects resting heart rate of the animal, highlighting the importance of maintaining and recording conditions. The protocols presented here do not require advanced engineering, fabrication, or software skills, and provide an approach to accurately record and report experimental conditions.