Swimming in an Oligochaete (Lumbriculus)
(Genus & species: Lumbriculus variegatus; Common name: California blackworm)
CONTROLLING THE ANIMATION:
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 frame 0) of the worm's head end (at left) as it swims through water. [NOTE: Each frame of motion represents 1/30th second of elapsed time, as indicated on the image by 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 6/30 sec interval (=1/5 sec). Express swim velocity in units of mm/sec. How fast does the worm swim in terms of body lengths per second? Compare your values to those of other annelids, such as leech..
3) Place another transparency sheet over the animation so that the worm image is centered near the top edge of the sheet. Advance the animation to frame 0 and carefully make a tracing of the worm's overall body shape. Label this first tracing "f 0". Next, advance the animation to the next frame and shift the position of the transparency sheet about 3 cm upward. Make another tracing of the worm's body shape just below the first and label this second tracing as "f1". Repeat this procedure until you have a series of at least six consecutive, stacked tracings, the first being at the top and the last at the bottom.
4) These traced images should show that the worm's forward locomotion is accomplished by production of a series of rhythmic, undulatory waves. Describe the shape of these waves. In what direction do the waves appear to move - - toward the worm's head, or toward the tail?
5) Use the tracings you just made to estimate wave frequency. This is done by first determining the elapsed time (in 30ths of a sec) per one wave cycle. Next, convert this value to wave frequency by inverting the fraction and expressing in units of cycles/sec.
Click here to see non-interactive GIF animation
Software for controlling interactive animations was developed by TOM DREWES