Phylum Nematoda: The Roundworms Roundworms Common name for

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Phylum NematodaThe Roundworms
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Roundworms

• Common name for phylum Nematoda is roundworms.
• They are among the most numerous of all animals.
• A single rotting apple can contain as many as
  90,000.
• Pseudocoelomates (pseudo false)
• No true coelom.
• They do have the peritoneal cavity (or gut), but
  it is not lined with mesoderm.

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Nematode Thread?

• Roundworms got their name nematode because they
  resemble a thread.
• In Greek, nematos actually means thread
• About 20,000 described organisms

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What is a Roundworm?

• Slender, unsegmented worms.
• Microscopic or up to a meter in length.
• Most are free-living
• inhabiting soil, salt flats, aquatic sediments,
  and water from polar to tropical regions.
• Parasitic
• Live in hosts
• almost every kind of plant and animal.

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What is a Roundworm?

• The effects of nematode infestation on crops,
  domestic animals, and humans make this phylum one
  of the most important of all parasitic animal
  groups.
• Almost all species of vertebrates and many
  invertebrates serve as hosts for one or more
  types of parasitic nematodes.

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Digestion

• Unlike the platyhelminthes, nematodes have a
  digestive tract with two openings.
• The body plan is called a tube-within-a-tube.
• The outer tube is the body wall and the inner
  tube is the digestive tract.
• Food moves in one direction through the digestive
  tract.

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Form and Function in Roundworms

• Roundworms have specialized tissues and organ
  systems that carry out essential body function.
• In general, the body systems of free-living
  roundworms tend to be more complex than those of
  parasitic forms.
• Distinguishing characteristics of this phylum are
  their cylindrical shape, flexible nonliving
  cuticle, lack of motile cilia or flagella, and
  the muscles of their body wall run only
  longitudinally.

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Body Covering

• Outer body covering is a thick, non-cellular
  cuticle secreted by the underlying epidermis, or
  hypodermis.

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Feeding

• Most free-living roundworms are predators
• carnivores that use grasping mouthparts and
  spines to catch and eat other small animals.
• Some soil-dwelling and aquatic forms eat algae,
  fungi, or pieces of decaying matter.
• Other nematodes digest the bacteria and fungi
  that break down dead animals and plants.

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Respiration, Circulation, and Excretion

• Like flatworms, roundworms exchange gases
  (respire) and excrete metabolic wastes like urea
  and ammonia through their body walls. (diffusion)
• They have no internal transport system.

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Response

• Nematodes have simple nervous systems, consisting
  of several ganglia.
• Several nerves extend from ganglia in the head
  and run the length of the body. These nerves
  transmit sensory information and control
  movement.
• Roundworms have several types of sense organs.

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Response

• A ring of nerve tissue and ganglia are found at
  the anterior end of their bodies.
• They have a pair of amphids
• more complex sense organs that open around their
  heads.
• They have a pair of phasmids
• similar in structure as amphids, but open around
  the posterior end of the body.

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Movement

• Muscles of nematodes extend the length of their
  bodies.
• Together with the fluid in the pseudocoelom,
  create a hydrostatic skeleton.
• A hydrostatic skeleton is the use of coelom fluid
  to maintain the shape of the animal and allows
  for movement.
• Aquatic roundworms contract these muscles to move
  like snakes through the water.
• Soil-dwelling roundworms push their way through
  the soil by thrashing around.

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Reproduction

• Roundworms reproduce sexually.
• They reproduce using internal fertilization.
• Female has ovary, passes them to the uterus,
  where they are fertilized.
• Male Sperm cells made in the testis and stored
  in the vas deferens.
• the male usually deposits sperm inside the
  females reproductive tract.
• Over 200,000 eggs can be deposited at once in the
  soil once they are fertilized.

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Reproduction Cont.

• Parasitic nematodes often have complex life
  cycles that involve two or three different hosts
  or several organs within a host.

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Anatomy
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Classes of Nematoda

• Two main classes
• Class Rhabditea they are both free-living and
  parasitic forms.
• Class Enoplea mostly free living, but includes
  some parasites.

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Roundworms Disease

• Many nematodes are very important pathogens of
  humans and domestic animals. Some of the
  nematodes we will discuss
• Hookworms
• Trichina Worm
• Pinworms
• Filarial Worms

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Trichina Worm

• They infect humans, hogs, rats, cats, and dogs.
  Hogs can become infected eating uncooked scraps
  of infected meat or rats.
• Heavy infections can cause death but lighter
  infections are more common.
• About 2.4 of the U.S. population is infected,
  mostly lightly.

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Trichinosis - cysts within the muscles are
consumed (undercooked food) -- worm grows in
intestine-- forms cysts in the muscles of the
new host -- symptom terrible pain in muscles
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Filarial Worms

• 8 species of filarial nematodes that infect
  humans.
• About 250 million people in tropical countries
  are infected with Wuchereria bancrofti or Brugia
  malayi, which live in the lymphatic system.
• They cause inflammation and blockage of the
  lymphatics.
• Females can be as long as 100 mm and can release
  live young, or tiny microfilariae into the blood
  and lymph.

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Filarial Worms cont.

• Mosquitoes ingest the microfilariae when they
  feed. The worms develop to the infective stage
  while inside the mosquito and move into the
  mosquito bite wound when it feeds.

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Filarial Worm Diseases

• Filarial worms cause three main diseases in their
  definitive hosts
• Elephantiasis
• River blindness
• Dog heartworm

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Ascarid Worms (common roundworm) - lives in
intestine- eggs are passed out in the feces
Most roundworms infect dogs, but occasionally
they find their way into human hosts
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Hookworms

• Hookworms are so named because the anterior
  (head) end curves dorsally, resembling a hook.
• They have large plates in their mouths that cut
  into the intestines so that they can suck on
• the hosts blood.

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Hookworms cont.

• Hookworms suck more blood than they can digest.
  A heavy infection can cause anemia.
• Eggs pass in feces and juveniles hatch in soil
  where they can live off of bacteria.
• If human skin comes in contact with the soil,
  infective juveniles burrow through the skin to
  blood.
• Bare foot, I think not!!!

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Pinworms

• Pinworms are the most common worm parasite in the
  U.S., but causes little disease.
• It is estimated that 30 of children and 16 of
  adults in the U.S. have them.
• Adults live in the large intestine and cecum.

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Pinworms cont.

• Females, about 12 mm in length, migrate to the
  anal region at night and lay eggs, causing
  itching.
• Scratching the anal region contaminates hands and
  bedclothes.
• So how do you test for something like this?

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Scotch Tape Method

• Fecal examinations and finding the eggs, but eggs
  are often not found in feces.
• Many times the female pinworm will deposit her
  eggs on the skin around the anus. Doctors have
  started using the scotch tape method.
• Truth is in fact stranger than fiction.

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Scotch Tape Method

• The scotch tape method consists of placing the
  sticky side of cellulose tape onto the anus
  overnight.
• The next morning the tape is umm...harvested and
  placed under a microscope to search for eggs.
• Drugs are effective against it,
• all members of the family should be treated at
  the same time because the worms spread easily
  through a household.

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Pinworms

• Eggs develop rapidly and become infective within
  six hours at body temperature.
• When swallowed, these eggs hatch in the anterior
  end of the small intestine (the duodenum) and
  mature in the large intestine.