Presentations today:
Derek/Travis
Nick/Dustin
Rachel/Arianne
Erica/Jordan
David/Dalton
Colton/Taylor
Katie/Dylan
Dewayne/Ciera
PHYLUM
NEMATODA
“The Roundworms”
Nematoda (Roundworms)
• widely distributed
• living in soil, animals,
• fresh and marine water
• Most are free-living
• many are parasitic.
Roundworm
Nematoda (Roundworms)
• tapered at both ends
• no segments
• thick outer covering = Cuticle
•
protects them in harsh environments
– Stomach acid
• Covering is shed 4 times as they grow.
Tapered ends
Round body
shape
Nematoda (Roundworms)
• no circular muscles
• lengthwise (longitudinal) muscles
• one muscle contracts
• another muscle extends
• causes them to move in a thrashing motion
from side to side
Nematoda (Roundworms)
• Have a pseudocoelom
• simplest animals with a one way
digestive tract – mouth to anus
Intestine
Mouth
Round body
shape
Anus
Nematoda (Roundworms)
• Eyespots very reduced in parasitic
roundworms.
• Approximately half of species are
parasites
• about 50 species infect humans.
Examples:
Ascaris, Pinworms, Trichenella, and
Hookworms
Ascaris
• the most common roundworm infection in humans
• children infected more often than adults
– Why?
• Eggs in soil
– enter through the mouth of humans
Life Cycle-– hatch in intestines
– move into bloodstream
– eventually to lungs
– coughed up
– swallowed
– begin the cycle again.
Pinworms
• most common human roundworm parasites in U.S.
• highly contagious
• eggs can survive for up to two weeks on surfaces
• live eggs ingested
• mature in host’s intestinal tract
• female pinworms exit host’s anus – itching!
• lay eggs on nearby skin
• eggs fall onto bedding or other surfaces
• Reintroduced to intestine by mouth
Trichinella
• Trichinella causes a disease called
“trichinosis”
• Found in raw or
undercooked meat
• Can be sexually
transmitted
Trichinella
Hookworms
• common in humans in warm climates
• Obtained when walking barefoot on
contaminated soil
• Hookworms cause
people to feel weak
and tired due to blood
loss.
Roundworm Parasites
• Nematodes can infect and kill pine trees, cereal crops,
and food plants such as potatoes.
• They are particularly attracted to plant roots and cause
a slow decline of the plant.
• They also can infect fungi and can form symbiotic
associations with bacteria that help plants obtain
nitrogen from air
• Nematodes also can be used to control pests
• Life on Earth is very dependent on nematodes
• Billions of nematodes in every one - symbiosis