Phylum Nematoda

Phylum Nematoda
The Roundworms
Phylum Level Characteristics
• round, not flattened
• no segmentation
• complete digestive system
– (2 openings: mouth and anus)
• -soft bodied, hydrostatic skeleton
• -bilateral symmetry
• No circulatory system
– Nutrients and wastes diffuse through body cells
Nervous System
• Exhibit cephalization as they have a
“head” end
• In head are several ganglia or nerve
bundles, no real “brain”
• Have sense organs that detect chemicals
given off by prey or hosts
• Longitudinal muscles so movement is
• Sexual
• Most species have separate males and
females, a few are hermaphroditic
• Fertilization occurs within the female
• Parasitic life cycles can involve many
• most are free-living
• found in all habitats
• very successful (high # of species and
large #’s of them)
• parasitic round worms also infect most
kinds of animals and plants
• -i.e. Ascaris infects
Ascaris Life Cycle
• Adult worms live in intestines
– Produce many eggs that leave in hosts feces
• Feces contaminated food or water eaten by
another host
– Eggs hatch in intestine of new host
– Young worms burrow into the walls of the intestine
and enter surrounding blood vessels
– Carried by blood, worms end up in lungs
– Travel up air passage into throat then are swallowed
– Carried back to intestines where process begins
ascaris animation
• -i.e. hookworm can enter body through
bare feet
Hookworm Life Cycle
• Hookworm eggs hatch and develop in soil
• Use sharp teeth and hooks to burrow into feet
• Continue burrowing until they enter the
• Travel to lungs, coughed up and swallowed to
eventually reach intestines
• Adult worms dig into intestinal wall and suck
blood of host
1. Watch Nematoda video
2. Complete nematoda worksheet
3. Complete nematoda flash cards!
Please remind me that we need to catch up
on the “ecological significance” notes for
the last 2 phyla!!