Measuring Complex Behavior Patterns in Fish—Effects of Endocrine Disruptors on the Guppy Reproductive Behavior

ABSTRACT

An obstacle in behavioral research is in obtaining unbiased measurements and presenting them in numerical terms, independent of human interpretation and observational endurance. Simple locomotory behavior can be relatively easily quantified with existing computerized vision systems, whereas it is much more difficult to obtain unbiased measurements of complex behavior patterns. We have developed a computerized vision system (DISPLAY), which identifies and quantifies complex behavior patterns and interactions in fish. In short, the fish scenery is viewed from above by a camera. At a frame-rate of 12 s^{− 1}, the fish silhouettes are stored in a frame file. Subsequently, the position and orientation of each fish relative to the other(s), the distance between them, and their body curvature are determined in each frame. Further, frame-to-frame comparisons enable calculation of speed and direction of fish movements. With these measurements available, composite behavior patterns can now be entered graphically by the user as distinct classifiers. The system has been used for studying the effects of endocrine disruptors on the reproductive behavior of the male guppy (Poecilia reticulata). Both estrogenic and antiandrogenic substances significantly suppress the number and duration of posturing behavior and sigmoid displays, two distinct elements in the courtship behavior of the male guppy.

Key words:

• quantification of fish behavior
• computerized vision system
• automatic measurements
• guppy courtship behavior

ACKNOWLEDGMENT

This work was supported by the Danish Natural Science Research Council.