Biol 212 Zoology Lab 07: Phylum Nematoda (10 points)

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1 Biol 212 Zoology Lab 07: Phylum Nematoda (10 points) Introduction All members of the clade Protostomia can be divided into the Spiralia and the Ecdysozoa. The synapomorphic characteristic of the clade Spiralia is that all members exhibit spiral cleavage during embryonic development. The synapomorphic characteristic of the clade Ecdysozoa is that they undergo ecdysis, the shedding of their outer skin, cuticle or exoskeleton during growth. An important member of the Ecdysozoa is the phylum Nematoda. The phylum Nematoda, or round worms, include about 16,000 described species, though there may be over a half-million species total. Many are free living, but most are parasitic, with many causing important diseases. Nematodes are perhaps the most widespread phylum; besides being found as parasites in both plants and animals, nematodes are found in Antarctice ice, moist soils, freshwater muds, in plant and algal mats, and in the bottom of the sea. The purpose of this lab is to introduce you to the phylum Nematoda. *On the upper, right-hand corner of your lab report, print your name, Biol 212, Lab 7: Phylum Nematoda, and the date you did this lab. Introductory Objectives Objective 1: Give the synapomorphic characteristic of the clades Spiralia and Ecdysozoa. Objective 2: Justify why we think that there may actually be a half million (or more) nematode species. Write out these questions then answer them: 1. What is the synapomorphic characteristic unifying organisms within the clade Spiralia and within the clade Ecdysozoa? 2. Why do we think that there may be a half-million nematodes, or more? As suggested above, not only are there a lot of species belonging to the phylum Nematoda, but these nematode species are widespread, occupying diverse ecological niches. Free-living nematodes are very common in estuarine and deep-sea muds, in and around plant roots, pond detritus---virtually anywhere there is a little water. Many are parasites of plants, including important agricultural parasites, many are parasites of animals, including human parasites. The human and animal parasites are numerous. Putman/Pierce College Biol 212 Lab 07/ /Page 1

2 Pinworms (Enterobius vermicularis) infect some 400 million people globally, especially children. They live in the lower intestine, the females moving to the anus to lay eggs, which causes severe itching. Eggs are spread to the environment by hand contact with the perianal area. Trichina worms (Trichinella spiralis), which cause trichinosis, may be picked up by eating undercooked pork, or undercooked meats from wild animals such as bear, walrus, cat and dog. The worm then migrates from the gut of the human that ate it into the muscle tissue, where it forms calcified cysts. Worms may also infect brain and heart muscle tissue. Inflammatory reactions commonly cause death. Hookworms (Necator americanus), infect humans by burrowing in through the feet as you walk onto moist soil; they are found in about 4% of the population in the Southern United states. Juveniles travel through the bloodstream to the lungs and burrow into the alveoli. The infected human then coughs, bringing up a bolus of worms, which are then swallowed. The worms mature in the intestines, passing their eggs into the feces. In the intestines, they feed on blood to the point where they may cause iron deficiency anemia, stunting of growth and lowered intelligence. Guinea worms (Dracunculus medinensis), are picked up from the guts of copepods, tiny arthropods, as contaminated water is consumed. As the copepods are digested, the Guinea worms are released and migrate from the digested copepods to the fat tissue just under the skin, tunnelling to the lower legs of the victim. Here, the female worm, which may be a meter in length, extends her posterior from the leg to lay eggs directly into the environment, usually water that the victim is standing in. The end of the worm can then be seized, and slowly pulled from the body. Filarial worms (Wuchereria bancrofti) are spread by mosquitoes in the tropics, are very thin worms up to a meter in length that block human lymph nodes and create grotesque disfigurements of the body, lymphatic filiariasis. Roundworms (Ascaris lumbricoides) may reach 40 cm in length in human intestines, where they live. Here, they feed on intestinal contents and occasionally blood from the intestinal lining. Heavy infestations can cause intestinal blockage, abdominal cramps, and other problems. Over two billion people worldwide are infected with Ascaris lumbricoides! Half of the people in the southeastern United Staes may be infected with the parasite. There are many other parasitic nematodes; in fact, over 50 species of parasitic nematodes infect humans alone. Virtually every species of animal and plant has nematode parasides. The life cycle of Ascaris lumbricoides, one of the most important parasitic nematodes, will serve to represent a general nematode life cycle. (See Fig. 7.1.) Adult worms live in the small intestine where the females lay eggs, which are passed out of the host in feces. Eggs are then ingested into the next host through contaminated food, such as insufficiently-washed produce, hand to mouth contact, eating dirt, or other ways. In the small intestine, eggs hatch and juvenile worms burrow through the lining of the intestine into the circulatory system. From there, juvenile worms are carried to the alveoli of the lungs, where they burrow out of the circulatory system into the alveolar air spaces. They then migrate up the trachea, facilitated by the coughing reflex, and are then swallowed down the esophagus. The esophagus carries them to the stomach. From the stomach, they proceed to the small intestine, where they mature. Of note: A. lumbricoides eggs can live longer than 10 years, can survive 2% formalin solution, 50% laboratory acid solutions, and can even be carried on banknotes. (So, wash your hands after Putman/Pierce College Biol 212 Lab 07/ /Page 2

3 handling money!) Fig. 7.1: Life cycle of Ascaris lumbricoides. Ex. Roberts and Janovy As in most nematodes, there is strong sexual dimorphism between male and female Ascaris lumbricoides worms. Females may be to 40 cm, males to 31 cm in length; males also have a hooked posterior containing spicules whereas females do not. During copulation, the male uses the spicules to keep the female s vulva open. In the female, ovaries, which make ova, are very long, convoluted and filamentous structures. If the reproductive tract is carefully teased apart it can be seen that there are two ovaries, each ovary connected to a uterus. The uteri then come together like a Y to form the vagina. The vagina opens at the vulva, or external lips. Eggs are released from the vulva as many as 200,000 per day! In the male, there is a single testis, which produces sperm, that widens into a sperm duct (vas deferens), that then connects to the seminal vesicle. The seminal vesicle opens into a short ejaculatory duct, that empties into the cloaca. The cloaca opens into the environment via and anus. In the male, the cloaca is also connected to the rectum, thus serves as a common exit for the reproductive and digestive systems. The digestive system in both sexes is a simple tube. Beginning with the terminal mouth, Putman/Pierce College Biol 212 Lab 07/ /Page 3

4 food is passed through the pharynx into the intestine, where food is digested and absorbed. From the intestine, feces are transferred to the rectum. In the female, the rectum is connected directly to the anus, which releases feces into the outside world. In the male, as mentioned above, the rectum connects to the cloaca, which also receives sperm from the ejaculatory duct, which opens into the anus. In cross sections of the male and female Ascaris lumbricoides, the outermost layer, the cuticle, can be clearly seen. The cuticle is made mostly of collagen, and is periodically shed as the animal grows. This is a primary synapomorphic characteristic linking together members of the clade Ecdysozoa. The process of shedding is called ecdysis. The cast-off exoskeleton of a nematode, or arthropod, is called an exuvia. The cuticle is acellular, and is secreted by the underlying epidermis. The cuticle of A. lumbricoides makes it impervious to digestion. Beneath the epidermis and running with Fig. 7.2: Longitudinal section of Ascaris lumbricoides. Ex. Roberts and Janovy the length of the body are the longitudinal muscle fibers. Since nematodes lack circular muscles, they move by a thrashing back-and-forth, whip motion; in fact, one group of nematodes is called the whip worms. An interesting note is that the muscle fibers have extensions that go to and interface with the dorsal and ventral nerves; in most animals, the nervous system sends extension to the muscles fibers! Laterally, you should see the excretory canal; the excretory canal drains fluids from the spacious pseudocoel into an excretory pore, located ventrally. The intestine should be easy to find within the pseudocoelom, and should be the largest tubular structure. In both the male and female, most of the pseudocoelom will be taken up by reproductive structures. In the smaller male, the smallest tubules will be the testis, with the second smallest tubules being the sperm duct (vas deferens). In the female, the smallest tubules will be the ovaries, with the oviducts being second in size and the uteri largest. Putman/Pierce College Biol 212 Lab 07/ /Page 4

5 Objectives Objective 3: Give the common and scientific name of the following nematodes, gie their life cycle, state how they are spread to humans and state their importance to humans: pinworms, Enterobius vermicularis; trichina worms, Trichinella spiralis; hookworms, Necator americanus; Guinea worms, Dracunculus medinensis; filarial worms, Wuchereria bancrofti; and roundworms, Ascaris lumbricoides. Objective 4: State about how many nematode species infect humans. Objective 5: Outline the lifecycle of Ascaris lumbricoides. Objective 6: Identify a specimen or photograph of Ascaris lumbricoides to phylum, genus, species and sex. Objective 7: Identify the mouth, anus, spicules spicules and vulva on the external anatomy of an appropriate-sex Ascaris lumbricoides. Objective 8: In a dissection of a male Fig. 7.3: Cross section of Ascaris lumbricoides. Ex. Hickman and Katz Ascaris lumbricoides, identify the following: mouth, pharynx, intestine, rectum, anus, pseudocoelom, testis, vas deferens, seminal vesicle, ejaculatory duct, cloaca and spicules. Objective 9: In a dissection of a female Ascaris lumbricoides, identify the following: mouth, pharynx, intestine, rectum, anus, pseudocoelom, ovary, oviduct, uteri, vagina, genital pore. Objective 10: In microscope slides of cross sections of male and female Ascaris lumbricoides, identify the sex, cuticle, epidermis, dorsal nerve, ventral nerve, excretory canal, longitudinal muscle cells, pseudocoel, intestine, testis, vas deferens, ovary, oviduct and uterus. Objective 11: Define ecdysis and exuvia. Putman/Pierce College Biol 212 Lab 07/ /Page 5

6 Objective 12: Describe/recognize the characteristic motion of nematodes and give the reason for this motion. Objective 13: State what is unique about the nematode muscle fibers regarding their relationship to their nervous system. Objective 14: State what prevents A. lumbricoides from being digested. Objective 15: Identify Necator americanus to phylum, genus and species, from microscope slides of the adult. Objective 16: identify Trichinella spiralis to phylum, genus and species, from microscope slides of the adult. Write out these questions then answer them: 3. What are five habitats or places where you can find members of the phylum Nematoda? 4. Complete the following chart, giving the common name for each parasite, life cycle, importance of parasite to humans, and how the parasite is contracted (spread) to humans. Scientific Name Enterobius vermicularis Trichinella spiralis Necator americanus Dracunculus medinensis Wuchereria bancrofti Ascaris lumbricoides Common Name Life Cycle Importance to Humans How Humans Contract Materials and Methods *Preserved Ascaris for dissection *Prepared microscope slides of Ascaris, male & female (cs) *Prepared microscope slides of Necator americanus *Prepared microscope slides of Trichinella spiralis *Prepared microscope slides of Wuchereria bancrofti -Dissection pan and equipment -Compound microscope 1. You and your lab partner should work together on this. I suggest wearing latex gloves. One Putman/Pierce College Biol 212 Lab 07/ /Page 6

7 of you obtain a male Ascaris lumbricoides, the other a female A. lumbricoides. Place them in a dissection pan and cover with water. You will also need fine scissors (or a scalpel), a couple of needle probes, forceps, and at least six dissecting pins. 2. Examine the external anatomy of the male and female. Draw the male accurately, as per the For the Lab Report boxes below. Identify and label the following structures: mouth, anus, spicules. Draw the female accurately, as per the For the Lab Report box below. Identify and label the following structures: mouth, anus and vulva. Include a size rule in both drawings 5. Write out, 5. Phylum Nematoda, Ascaris lumbricoides, male, external anatomy. Identify, draw and label the mouth, anus and spicules. Include an accurate size rule in cm next to your drawing. No credit for drawings without accurate size rules. To the right of yur drawing, state how big the size rule is in millimeters (for example, Size rule = mm. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! 6. Write out, 5. Phylum Nematoda, Ascaris lumbricoides, female, external anatomy. Identify, draw and label the mouth, anus and vulva. Include an accurate size rule in cm next to your drawing. No credit for drawings without accurate size rules. To the right of your drawing, state how big the size rule is in millimeters (for example, Size rule = cm. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! 3. Now, take your A. lumbricoides and locate the middorsal line. Beginning just to the left or right of the middorsal line, pierce the animal with your fine-point dissecting scissors and pull up slightly and begin to cut, so that you don t damage the internal organs. As you re doing this, pin the sides of the worm open to the wax of the dissecting pan; slant the pins outward so that you fully expose the pseudocoelomic cavity. With great care and patience, tease out the reproductive and digestive structures without breaking them. 4. Draw the dissected male A. lumbricoides. Identify and label the following structures: mouth, pharynx, intestine, anus, pseudocoelom, testis, vas deferens, seminal vesicle, ejaculatory duct, cloaca, spicules as per the For the Lab Report box below. 5. Draw the dissected female A. lumbricoides. Identify and label the following structures: mouth, pharynx, intestine, rectum, anus, pseudocoelom, ovary, oviduct, uteri, vagina and vulva as per the For the Lab Report box below. Putman/Pierce College Biol 212 Lab 07/ /Page 7

8 7. Write out, 7. Phylum Nematoda, Ascaris lumbricoides, male, internal anatomy. Draw the internal anatomy of the male; as you are doing so, identify, draw and label the mouth, pharynx, intestine, anus, pseudocoelom, testis, vas deferens, seminal vesicle, ejaculatory duct, cloaca and spicules. Include an accurate size rule in cm next to your drawing. No credit for drawings without accurate size rules. To the right of your drawing, state how big the size rule is in centimeters (for example, Size rule = cm. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! 8. Write out, 8. Phylum Nematoda, Ascaris lumbricoides, female, internal anatomy. Draw the internal anatomy of the female; as you are doing so, identify, draw and label the mouth, pharynx, intestine, rectum, anus, pseudocoelom, ovary, oviduct, uteri, vagina and vulva. Include an accurate size rule in cm next to your drawing. No credit for drawings without accurate size rules. To the right of your drawing, state how big the size rule is in centimeters (for example, Size rule = cm. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! 6. Before you dispose of your Ascaris lumbricoides dissection, ask your instructor is he wants it. Otherwise, dispose of the dissection and gloves in the designated container; it would also be a good idea to wash your hands after handling Ascaris as the eggs may still be viable, although this is unlikely. Write out these questions then answer them: 9. What are the chief external morphological differences between male and female Ascaris? (In other words, how can you tell them apart?) 10. What is the difference in the placement of the openings of the reproductive organs? 7. Obtain your compound microscope. Obtain commercially-prepared microscope slides of cross sections (transverse sections) of male and female Ascaris lumbricoides (hopefully, on the same slide). 8. Draw the male cross section and identify and label the cuticle, epidermis, longitudinal muscle cells, lateral line, excretory canal, pseudocoel, ventral line, ventral nerve, testis, vas deferens and intestine as per the For the Lab Report box below. Putman/Pierce College Biol 212 Lab 07/ /Page 8

9 9. Draw the female cross section and identify and label the cuticle, epidermis, longitudinal muscle cells, lateral line, excretory canal, pseudocoel, ventral line, ventral nerve, ovary, eggs, oviducts, uterus and intestine as per the For the Lab Report box below. 11. Write out, 11. Phylum Nematoda, Ascaris lumbricoides, male, cross section. Carefully and accurately draw a cross section of the male A. lumbricoides. Identify, draw and label the cuticle, epidermis, longitudinal muscle cells, lateral line, excretory canal, pseudocoel, ventral line, ventral nerve, testis, vas deferens and intestine. No credit for drawings without accurate size rules. To the right of your drawing, include total magnification (for example, 40x ) and how big the size rule is in micrometers (for example, Size rule = m. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! 12. Write out, 8. Phylum Nematoda, Ascaris lumbricoides, female, internal anatomy. Draw the internal anatomy of the female; as you are doing so, identify, draw and label the cuticle, epidermis, longitudinal muscle cells, lateral line, excretory canal, pseudocoel, ventral line, ventral nerve, ovary, eggs, oviducts, uterus and intestine. Include an accurate size rule in cm next to your drawing. No credit for drawings without accurate size rules. To the right of your drawing, include total magnification (for example, 40x ) and how big the size rule is in micrometers (for example, Size rule = m. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! Write out these questions then answer them: 13. At least 50 species of nematodes occur in which animal? 14. Worldwide, how many humans are infected with Ascaris lumbricoides? 15. How could you get infected with Ascaris lumbricoides? 16. What are the symptoms of a heavy Ascaris infection? 17. Define ecdysis and exuvia. 18. What is the characteristic motion of nematodes? 19. Why do nematodes exhibit a characteristic motion? 20. State what is unique about the nematode muscle fibers regarding their connections with the nervous system. 21. What prevents Ascaris from being digested by the human gut? Putman/Pierce College Biol 212 Lab 07/ /Page 9

10 10. Obtain a microscope slide of Necator americanus. Draw the worm accurately, according to the For the Lab Report box below. 22. Write out, 22. Phylum Nematoda, Necator americanus. Draw Necator americanus. Include an accurate size rule next to your drawing. No credit for drawings without accurate size rules. To the right of your drawing, include total magnification (for example, 40x ) and how big the size rule is in micrometers (for example, Size rule = m. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! 11. Obtain a microscope slide of Trichinella spiralis. Draw the worm accurately, according to the For the Lab Report box below. 23. Write out, 22. Phylum Nematoda, Trichinella spiralis. Draw Trichinella spiralis. Include an accurate size rule next to your drawing. No credit for drawings without accurate size rules. To the right of your drawing, include total magnification (for example, 40x ) and how big the size rule is in micrometers (for example, Size rule = m. Also, include any notes that might help you to identify the organism on the lab practical! Have your instructor check and initial your drawings for credit; all drawings must be completed in lab and signed by your instructor for credit! 12. If living cultures containing nematodes are available, using a pipette, take a drop of culture containing some pond detritus and place it on a microscope slide. Locate a nematode and describe how it moves. 24. Write out, 24. Description of living nematode movement. Locate a living nematode in a pond culture. Observe and describe its movement. ~When you re finished, help clean up! 1. Is your lab bench clean and wiped down with antiseptic solution? 2. Are all materials returned to their proper place? 3. Is the oil immersion objective of your microscope clean? 4. Is the lowest-power objective of your microscope positioned down? 5. Is the power cord draped loosely about one of the oculars? 6. Is your microscope put away? 7. Is all refuse disposed of properly? 8. Is the lab generally in order? Putman/Pierce College Biol 212 Lab 07/ /Page 10