All the experiments are finished and we have now started to analyze the data, i.e. we finally measured the copepods velocities! Using specialized software, we tracked the movement of copepods in the images provided by the cameras. The position of copepods that stayed in focus within the field of view of the camera was captured in horizontal (X) and vertical (Y) coordinates by the software, frame by frame, and that way we obtained time series of positions for every copepod in every video.
Here you can see a tracked copepod. The circles show the positions of a copepod at time 1 (red) and time 2 (yellow) and the line crossing through the circles indicates the coordinates of these positions. The differences between the positions at the two times are indicated by the white lines. Based on those differences we calculated horizontal and vertical velocities, as we also know the time difference between frame 1 and 2. Finally, the width of the the injection port (0.8 cm) was used to transform coordinates to cm.
To see how the copepods behave we also looked at the shape of the trajectories as a whole…and observed striking differences in swimming behaviours between animals! Below you can see the most complex (left), and the simplest trajectory (right) of our experimental copepods.
Swimming paths of copepods. Red and blue circles show initial and final positions, respectively.
Those are exciting results for us, and if you speak Spanish you can hear more about the experiments and of other research in a radio interview of researcher Nicholas Weidberg.