Swimming in a daphnid
(Crustacea, Cladocera)

Wait for the animation to load completely and play through once. To stop the animation, click on the "pause" button. To see the frame that precedes the paused frame, press the "previous" button. To see the frame that follows the paused frame, click on the "next" button. To resume the animation, click on the "play" button.

1) Consult references to determine what anatomical structures the daphnid uses to swim. 
2) Lay a small clear transparency sheet over the animation. Use two small pieces of paper tape to secure corners of the transparency sheet to the monitor screen. Use a marking pen to make a series of dots on the sheet that track the frame-by-frame position (starting at frame 0) of the daphnid as it swims through water. [NOTE: Each frame of motion represents 1/30th second of elapsed time (0/30, 1/30, 2/30 etc)]. Make sure the correct elapsed time is recorded for each dot and make sure the distance scale is carefully recorded on the transparency sheet. Do the data points indicate that the daphnid swims in a straight path?
3) Compare the forward progress made with each 30th of a second of elapsed time. Is forward progress uniform for each 1/30th second interval? If not, explain why, using your understanding of daphnid anatomy and locomotion from question #1.
4) Remove the transparency sheet and lay it on a piece of white paper. Then, determine the forward velocity of swimming, as determined by computing the daphnid's forward progress during a 6/30 sec (=1/5 sec) interval. Express units in mm/sec. 
5) What is the daphnid's body length in mm?  How fast does the daphnid swim in terms of body lengths per second?

Click here to see non-interactive GIF animation
Software for controlling interactive animations was developed by TOM DREWES