Trajectory reconstruction begins by digitizing each video frame of a prey capture sequence, and overlaying a wireframe model of the fish using the graphical user interface shown below. The position and configuration parameters of the wireframe model are then used to reconstruct the 3-D trajectory of fish and prey. Now we can carry out detailed quantitative analysis of the behavioral strategies used by the fish. The image below shows a typical prey capture sequence reconstructed using this technique. The circle represents the Daphnia .
Time is in milliseconds relative to the time of prey detection.
We think this behavioral strategy is related both to biomechanical aspects of trying to rapidly close the gap to the prey, and sensory aspects of trying to optimize the electrosensory image, since the dorsal edge of the fish has a much higher density of electroreceptors than the lateral body walls. Using this approach, we've also shown that the range at which the Daphnia can be detected is a function of the electrical conductivity of the water, as would be expected if prey detection were mediated by the electric sense. This is one of the first direct demonstrations that the electric sense is involved in prey capture behavior in weakly electric knifefish. This is described in more detail in another section of the web site where we discuss computational aspects of our research, but as a preview, here's an picture showing reconstructed electrosensory images mapped onto the wireframe model.