Undulatory Swimming in a Nematode
(Genus Turbatrix aceti; common name "vinegar eels"

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) 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 the frame labeled 0/30) of the worm's head end (top) as it swims through vinegar. [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.
2) Remove the transparency sheet and lay it on a piece of white paper. Then, estimate the forward velocity of swimming, as determined by computing the worm's forward progress during a 5/30 sec interval (=1/6 sec). Express units in mm/sec. Compare your velocity values to those seen in a
leech or blackworm.
3) Attach a second transparency sheet over the animation so that the animation window is near the left edge of the sheet. Advance the animation to frame 0 and make a tracing of the worm's overall body shape. Label the tracing "0/30". Next, advance the animation to the next frame and shift the position of the transparency sheet about 2 cm to the left. Make another tracing of the worm's body shape and label it "1/30". Repeat this procedure until you have a series of at least six consecutive tracings, with the first image at the left and the last at the right.
4) The traced images should show that the worm's forward locomotion consists of undulatory, rhythmic waves. Describe the shape of these waves. In what direction do the waves move along the body?
5) Use the tracings you just made to estimate wave frequency.  This is done by determining the time interval (in sec) it takes to complete one full cycle of wave motion. Then, take the reciprocal of this value to obtain wave frequency, expressed in cycles/sec.

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