Worms

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Worms

• Biology
• Mrs. Volin

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Worms

• Sense organs, mouth at anterior
• Long, slender body allows rapid movement /
  control of direction
  
• Three phyla
• Flatworms
• Roundworms
• Segmented worms

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Phylum Platyhelminthes Flatworms
planarian

• Thin (few mm thick)
• Bilaterally symmetrical
• Single opening to pass food and waste
• Pharynx extends out to suck in food
• Free-living or parasitic

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Class Turbellaria Free-living flatworms

• Marine / freshwater
• Carnivores or
• scavengers
• Light sensitive
• eyespots
• Pharynx brings food into gastrovascular cavity

Planarian
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Class Trematoda Parasitic flatworms

• Flukes
• Infect internal organs of host
• Some live on outside of host

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Schistosomiasis ---Blood fluke

• Affects 200 million people

Schistosoma egg in liver
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Schistosomiasis
larvae
Eggs clog blood vessels in liver, spleen, lungs,
intestines
Intermediate host
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Class Cestoda Tapeworms

• Parasitic flat and long
• Need no digestive system

scolex
proglottids
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Taenia

• Tapeworms can grow to several meters in length in
  the intestine

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Tapeworm life cycle
tapeworm attaches inside host intestine
zygotes
larval cysts
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Phylum Nematoda Roundworms

• Free living or parasitic
• Digestive tract has two openings

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Disease-causing roundworms Trichinella

• Transmitted by consuming improperly cooked pork
• Trichinosis

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Disease-causing RoundwormsElephantiasis

• Worm infects blood and lymph vessels
• Transmitted by mosquitoes
• Tropical parts of Asia

Swelling caused by blockage of lymph vessels
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Disease-causing RoundwormsAscaris

• Parasitic roundworm
• Affects humans, cats, dogs, horses, pigs,
  chickens
  
• Cause severe malnutrition
• Spread by eating food or water contaminated with
  Ascaris eggs

Intestine filled with Ascaris
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Hookworms
Necator
Hookworms penetrate the bottoms of bare feet. Do
not go barefoot.
This patient presented with a hookworm infection
involving the toes of the right foot, which is
also known as ground itch. Usually the first
sign of infection is itching, and a rash at the
site where skin touched contaminated soil or
sand, which occurs when the larvae penetrate the
skin, followed by anemia, abdominal pain,
diarrhea, loss of appetite, and weight loss..
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Pinworm (Enterobius)
0.5 inches long
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Guinea Worms
Dracunculus medinensis
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Guinea Worms
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Phylum Annelida Segmented Worms

• Body divided into segments by internal walls,
  septa
  
• In many annelids, segments specialize for
  specific function
  
• Eyes
• Antennae
• Respiration
• Example earthworm
• (See page 697 in text)

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• Examples to know
• Phylum Platyhelminthes (flatworms)
• Planarian, free living
• Tapeworm, parasitic
• Flukes ex. Schistosoma, parasitic, causes
  Schistosomiasis
  
• Phylum Nematoda (roundworms)
• Trichinella, parasitic, causes trichinosis
• filarial worms, parasitic, causes
  Elephantiasis (filariasis)
  
• Ascaris, parasitic
• hookworms, parasitic
• pinworms, parasitic
• Guinea worms, parasitic
• Phylum Annelida (segmented worms)
• earthworm, free living
• Nereis, free living