DESCRIPTION

Precision Activity Measurement for Small Animals

The AD-2 activity detector is specifically designed for small animals and small spaces – monitoring changes in position using invisible infrared light (880 nm at very low power) that will not affect the organism’s behavior. It is available with a fixed, reflective detector (AD-2) or with a probe pair that can be placed in any orientation (AD-2-1) for either direct or reflected infrared light. This versatile optically-based motion detector is ideal for creating an index of activity or for monitoring specific areas for activity.

Activity detectors are useful for separating episodes of activity and inactivity for behavioral assays and especially for respirometry. If you are trying to measure the inactive or “resting” metabolic rate of any animal, activity will corrupt your measurements. The AD-2 activity detector provides an objective determination of activity that can be recorded as a voltage signal, which is essential to research-grade respirometry for small animals such as insects.

A holder for our RC-M miniature respirometry chamber is supplied standard. The AD-2 activity detector uses uncritical 9 – 18VDC at very low power (< 30 mA).  In the case of multiple-animal respirometry systems, the Sable Systems RM-8 flow multiplexer can direct the electrical signal from the appropriate AD-2 to a data acquisition system.

How does it work?   

The AD-2’s principle of operation is IR source, light-based. The subject animal is contained in an RC-M precision respirometry chamber, which has transparent walls and two reflective metal end-pieces. The transparent glass envelope of the chamber encloses an animal surrounded by two curved reflective surfaces.

These reflectors have slight random surface irregularities that randomly disperse reflected light throughout the chamber. Fluctuations in the reflected light intensity are amplified and converted to voltage fluctuations. The chamber and reflectors are sealed to eliminate the influence of ambient light fluctuations on the signal. The activity detector’s own light source is in the near-infrared (~900 nm
wavelength), which has very low intensity in most laboratory environments, further minimizing interference. This light is undetectable to all known arthropods, and is of too short a wavelength and too low a power to cause significant heating effects.

The instantaneous (in Green) and cumulative activity (in Blue) of a single dung beetle undergoing a thermal ramping treatment (in Red). Note the magnitude and frequency of spontaneous activity increased with temperature, peaking around 40C. Thereafter activity levels tend to decrease.

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