|Worms - Advanced|
| General Conference
|| Skill Level 2
Year of Introduction: 2006
1. What are the 3 major classes of platyhelminthes and describe them.
The Monogenea, Trematoda, and Cestoda are the three major classes of parasitic flatworms, though the Turbellaria used to be considered a part of this class*
Monogeneans are largely ectoparasites on vertebrates like fishes; trematodes are the flukes, most of which live inside the organs of a variety of vertebrates as adults; and cestodes are the tapeworms, living in the intestines of a variety of vertebrates as adults (this is why your pets get annual shots—so that they don’t experience cestodes or trematodes—otherwise, pets could die as a result of an infestation of these worms.)
All Platyhelminthes are hermaphroditic in nature, meaning they can fertilize themselves.
- Turbellarians are, for the most part, free-living and non-parasitic, and thus do not in reality conform consistently with the rest of this class which is parasitic in nature.
For sake of completeness, it should be noted that the Monogenea are listed only on the most recent, scientific websites as part of the platyhelminthes classification. Most websites still refer to the pre-1999 classification of the platyhelminthes, making Turbellaria a class within that classification.
2. Name an example of a nematoda and describe its lifecycle.
Nematodes are also known as roundworms or eel worms. Examples include Lungworms, Hairworms, the Potato cyst, and stomach worms.
There are hundreds of types of nematodes.
There are three types of lifecycles present simply in the portion of this classification that infect plants:
Nematodes that are migratory ectoparasites are those that find plants as hosts (plant-parasitic). Migratory ectoparasites only feed on the surface cells of the plant (they don’t burrow into the plant). Pin, ring, and mint nematodes are examples of this type of nematode.
Their lifecycle: Eggs are laid only in the soil and develop until a first stage juvenile nematode is present. This nematode molts for the first time while still within the egg and it is the second stage juvenile which emerges from the egg into the soil. Moving through the soil, this nematode finds a root and inserts its stylet into one of the surface (epidermal) cells on the root surface. After feeding for some period of time, the nematode withdraws its stylet and moves on to feed in a new location. When the nematode has grown to a certain size, it molts a second time to become a third stage juvenile and later a third time to become a fourth stage juvenile. After a fourth and final molt, the nematode becomes an adult.
Migratory endoparasites are similar to the Migratory ectoparasites, except for the fact that they burrow into the plant to feed. Migratory endoparasites lay the eggs inside the host plants. The first stage juvenile molts inside the egg. The egg hatches once the juvenile has entered its second stage. Once released into the cortex (inside) of a plant, the juvenile will molt three more times, becoming either male or female. The eggs of the female will be laid in the cortex of the plant host. At any stage, juveniles may move to (hence the term migratory) and infect new plants.
Sedentary endoparasites enter their host species setting up a permanent feeding station. Eventually a mature female will lay her eggs inside the host plants. The first stage juvenile molts inside the egg. The egg hatches once the juvenile has entered its second stage. This second stage is the ONLY stage that is infectious. It will leave the host plant and burrow into a plant, and release enzymes that change the chemical composition of the plant cells surrounding it. These adapted cells become the embedded nematodes food source as it grows into a sausage shape, entering stages 3 and four and eventually laying its eggs before dying. http://ippc2.orst.edu/mint/nemacycle.htm
Hairworm life cycle: The hairworm eggs hatch in water releasing stage to juvenile stage hairworms. Grasshoppers are their eventual host, though scientists are sure how the hairworm larvae get inside the grasshoppers. Eventually, through several moltings, the larvae that have gotten inside the grasshopper fill the grasshoppers whole body cavity releasing a toxic mixture of chemicals that causes the grasshopper to commit suicide by jumping into water. Once the grasshopper parasite host is dead, the adult hairworm emerges from the grasshopper, and repeats the lifecycle by laying a batch of eggs. http://news.nationalgeographic.com/news/2005/09/0901_050901_wormparasite.html
3. What are the three major classes of annelida and how do they move?
The three classes of annelids are Polychaeta (marine annelids); Oligochaeta (marine, freshwater and trrestiral annelids such as earthworms); Hirudinea (marine, freshwater, and terrestrial leeches).
The Polychaeta move with bristles (Setae) that extend out from parapods, side flaps that extend from their bodies. The bristles look and act similar to legs, and help the polycaet swim or burrow.
The Oligocaeta and Hirudinea move by contracting muscles in their body in a sequential fashion, forcing their coelomic fluid to change the shape of each segment, thus moving their body forward. The setae bristles assist in anchoring them as they move forward.
4. Answer the following:
a. Distinguish between the following body structures: coelomates, pseudocoelomates, and acoelomates.
All of the following body structures contain bilateral symmetry. That is, they are symmetrical alone a defined plane. One example of bilateral symmetry is that if a person looked in a mirror and imagined a line extending from the middle of his/her head down to the floor, the body on the left side of the line would be a “mirror image” of the part of the body on the right side of the line.
Coelomates have a complex body cavity. Organs are suspended from the body wall. Mollusks and humans are just a few of the animals that share this body structure. Pseudocoelomates have a simple fluid filled body. The organs of these simple animals often float within the body cavity. Nematodes are the most numerous members of animals that have this body structure. Acoelomates lack internal body cavities. Acoelomates include flatworms and ribbon worms. For example, flatworms have organs, but do not have a fully formed digestive tract or a way to transport oxygen through the body. Therefore, each cell is required to handle respiration individually. http://www.bookrags.com/Animal
b. Which body structures are common in the three phyla of worms?
1. Coelomates (segmented/annelida)
2. Pseudocoelomates (roundworm/nematoda)
3. Acoelomates (flat worm/platyhelminthes)
5. Be able to demonstrate three ways to purify water.
The following advise on how to purify water for drinking. Please note that this is general advice; before drinking any water, you should check with local authorities as to its suitability. Be cautious of water containing particulate or solids, or polluted with unknown chemicals.
According to the Red Cross, to purify drinking water use any of the following methods:
1) Boil for five to ten minutes
2) Add ten (10) drops of household bleach solution per gallon of water, mix well and let stand for thirty (30) minutes. A slight smell or taste of chlorine indicates water is good to drink.
3) Add household tincture of iodine in the same manner as bleach above.
4) Use commercial purification tablets, following package directions. Two commercial brand names as Halazone and Globaline
6. Complete the following:
Note: Such organizations as adra.org and worldwater.org provide information and resources for both parts of this question.
a. From what you have learned about worms. Why is the availability of fresh water so important to human health, especially in third world countries?
To get you started: Fresh water that is free of organisms, including the parasitic worms we have studied, assists persons in living longer, avoiding disease, and living higher quality lives.
b. Organize a fund raiser to support organizations that strive to provide freshwater to third world counties.
For fundraising ideas, visit the NAD Pathfinder Forum at http://www.pathfindersonline.org/forum/viewforum.php?f=9.
7. Describe a spiritual lesson about living water from the Bible.
John 4 contains the story of the woman at the well who received the instructions from Jesus about receiving living water. Consult the SDA Bible Commentary and your choice of Bible version (www.biblegateway.com) for the complete story. Also, Psalms 1:3 and Jeremiah 17:8