Locomotion in a Freshwater Oligochaete Worm
Total Page：16
File Type：pdf, Size：1020Kb
How-To-Do-It As the Worml Turns Locomotionin a FreshwaterOligochaete Wlorm Charles Drewes Kacia Cain Worms are generally perceived as behavior is called a central pattern Materials neither very manageable nor talented generator (Young 1989). Central pat- with respect to their locomotor abili- tern generatorsfor locomotionin anne- * Lumbriculusvariegatus (use several Downloaded from http://online.ucpress.edu/abt/article-pdf/61/6/438/49035/4450725.pdf by guest on 25 September 2021 ties. However, locomotion in black- lids and arthropodsare usually located blackworms/group).Sources are: worms may be an exception and, con- in the ventral nerve cord. Motor neu- (1) www.novalek.com/korgdel.htm sequently,we hope this articlechanges rons in the ventral nerve cord are (2) www.holidayjunction.com/aro/ such "wormy" perceptions. responsible for conveying impulses (3) www.carolina.com Blackworms, Lumbriculusvariegatus from the central pattern generator to (4) tropicalfish and pet stores. (Phylum Annelida, Class Oligochaeta), the specific muscles in the body that For additionalbiology background are common in wetlands of North produce locomotor movements. about Lumbriculus, see Drewes America. Unlike tubifex worms (dis- Many forms of rhythmiclocomotion (1996a,b) and Lesiuk & Drewes tant relatives that occupy tunnels in depend on the coordinated actions of (1999). muddy sediments), Lumbriculusfreely well-designed appendages. Other * Disposable petri dishes (150 x 20 crawls on submerged and decaying forms of locomotion require no mm): one-half dish/group vegetation, such as decomposing appendages,such as peristalticcrawling * Disposable petri dishes (60 x 15 leaves, logs and cattails.When touched in many terrestrial, freshwater and mm): one-half dish/group or threatened,it uses a variety of loco- marine annelid worms; or undulatory * Disposable petri dishes (100 x 15 motor responses to protect itself or swimmingin certain aquatic annelids, mm): Each student group will use move to safety. One of these responses, some nematodes, and some snakes one dish, which should be half- helical swimming, is a fascinatingand (Trueman 1975; Drewes & Fourtner unusual form of animal locomotion. 1993; Drewes 1999). filled with springwater and contain several worms. An early version of this exercisewas The experiments here focus on field tested by high school biology crawling and swimming behavior in * Filter paper disks (12.5-cmdiame- teachers at a 1996 Summer Institute Lumbriculusvariegatus, a freshwateroli- ter): one disk/group in Neurobiology (Woodrow Wilson gochaete worm. Many questions arise * Plastic dropping pipet (6"plain, or National Leadership Program for about the control and biomechanics eye dropper):one/group Teachers;Princeton, NJ). Also, we pre- of this worm's locomotion.Answering * Spring water (about 200 ml/ sented the material as a "hands-on" these will require your students to group).Most commercialbrands of workshop at the 1996 NABT meeting make close observations, repeated spring water (forexample, Evian", (Charlotte,NC). measures, and keen insights. NayaT, Poland Springs") are very "worm friendly." Have several large containers of spring water Background available. [NOTE:Well-aged and General Suggestions dechlorinatedtap water may be an Locomotionis crucial to animal sur- Lumbriculus,like many freshwater acceptable alternative to spring vival because it enables movement water in many cities. To test toward food or a mate, or away from invertebrates,may die if exposed to small amounts of chlorine, formalin, whether aged water is safe for unfavorable habitats or predators. worms, place two to three worms Often, locomotion involves rhythmic dishwasher soap residues, and many other lab chemicals. Make sure glass- in a small, covered containerof the movements, such as walking, running, water overnight and confirm that and 1968; ware, plastic ware, pipets, and other swimming flying (Gray worms are alive the next day.] Alexander 1982). The specific network items used in these experiments are * 51/2"x 7/8" or neurons in an animal's nervous free of these chemicals. If in doubt, Swim chamber(prefered: system that controls such rhythmic thoroughly rinse items with dechlori- disposable plastic weighing boats, nated tap water or spring water. For containing 100 to 120 ml of spring cleanup, wash and rinse items in tap water). For container strength, we CharlesDrewes is Professor of Zoology water using no soap. Items should be recommend stacking three weigh- and Geneticsat IowaState University, completely dry before reuse. ing boats together. Alternative Ames, IA5001 1; e-mail: cdrewes@ in small swim chambersshould be about 10 iastate.edu. Kacia Cain is Chairper- Students should work son of Science at East HighSchool, groups (two to three students/ group). to 20-cm diameter,2 to 4-cm deep, Des Moines,IA 50316. ExperimentsI and II require about 20 and have a smooth, light-colored to 30 minutes each to complete. bottom. 438 THEAMERICAN BIOLOGY TEACHER, VOLUME 61, NO. 6, JUNE1999 * Plain wooden applicator stick, or ExperimentI: Forward& of the marked dish (Figure 2B). With toothpick (two/ group) gentle handling, patience and practice * Rubber bands (narrow, size #19; RearwardCrawling you will get the worm to crawl around four/ group) A) Prior to class, use a permanent and around this track. If, by chance, * A few human hairs (straight, markingpen and flexible ruler to care- the worm roams far away from the coarse, about 1"-long;two/group) fully make a series of half-centimeter track,or begins crawlingoff the paper, * Maskingor label tape (severalrolls) marks around the outside edge of a don't panic or force the worm back * Coins (about 2 to 3/group; not 6-cm plastic petri dish. Number whole into position! Simply, tilt the crawling for betting) centimeter marks consecutively so platform slightly, and use one or two * Whiteunlined paper (as light back- numbers can be read when the open pipets full of spring water to flush the ground under worm containers) side of the dish is facing down (see Fig- worm off the paper and into the runoff * Metricrulers (flexible vinyl, 15-cm ure 2A). water at the edge of the dish. Then, length; one / group) B) Place a 150-mmpetri dish on the suck up the worm, deposit it again next to the track. Tilt the dish and * Stop watch, wristwatch, or room counter top with its open side facing up; this dish is the crawling platform. remove excess water. Then, add back clock (must show seconds) 4 ml of spring water, as described * Permanentmarking pens (narrow Next, center a 12.5-cmfilter paper disk in the dish and saturateit completely above in Step D. Worms may be tip; one per group) unwilling to stretch out and crawl if * Scissors (to cut rubber bands and with spring water. a worm as the filter paper is too dry. tape; several per class) C) Assemble "racetrack" shown in Figure 2A. The coins, taped G) Study forward and rearward Downloaded from http://online.ucpress.edu/abt/article-pdf/61/6/438/49035/4450725.pdf by guest on 25 September 2021 * 10-ml graduated cyclinder (one/ to the centerof the inverted inner petri crawlingmovements around the track. group) dish, provide an elevated surface that To evoke forward crawling,very gently is higher than the edge of the outer stroke tail segments with the rubber tip. To evoke rearwardcrawling, gently Optional Materials dish. The rubber bands, crisscrossed over the coins, provide downward stroke head segments. During crawl- pressure to firmly hold the open face ing, note areas where the worm's body * Stereo dissecting microscope of the inner dish against the paper. appearsthicker and darker(Figure 2B). (one/group) This prevents worms from crawling In these areas, segments have short- * Pipe cleaners or solid-conductor, under the edge of the inner dish, which ened, due to longitudinal muscle con- insulated wire for models of swim- is undesirable. traction. Note also that these areas ming worms D) Use a pipet to transfer a worm move, as a wave, along the body in * Wooden dowels (/4, 5/16, and 3/8") for from the 10-cm storage dish onto the a direction opposite the direction of models of crawling worms filter paper on the crawling platform, locomotion. * Video camcorder close to the inner dish. Tilt the crawl- * Tripod ing platform at a 450 angle and use [Note:Upon request, authors will provide and * Adjustablelighting the pipet to remove the accumulated neurobiologybackground information water at the edge of the dish. Then, answers to the following two question add back 4 ml of spring water to the sets]. paper, thus insuring that the paper Assembling WormWidgets will be sufficientlysuper-saturated for & Racetrack good crawling performance by the Questions About Crawling worm. Cl) Give possible reasons why the Touch stimuli readily evoke locomo- E) Now, make sure you can distin- worm usually crawls in a circularpath tion in Lumbriculus.However, since guish between the worm's head and around the dish rather than in a worms are easily damaged by sharp, tail. The head end is darker, thicker, straight line. rigid objects, small probes (widgets) and generally more active. The tail is C2) In what direction do peristaltic will be used to harmlessly touch light-colored, thin, and less active. waves of contractionmove along the worms. Carefully assemble each wid- F) Use the tip of the straightrubber worm's body as it crawls forward?In get by taping pieces of rubber band widget to verygently touch the worm's a head-to-taildirection? Or tail-to-head and hair to applicatorsticks, as shown head or tail end until it begins crawling direction?In what direction do waves in Figure 1. forward or backwards along the edge move during rearward crawling? C3) Since peristaltic waves are rhythmicand repetitive,try to measure the time (in seconds) between two straight looped straight looped successive waves as these move hair hair rubber rubber throughone specificbody region, such as 1 cm posterior to the head end.