Transcript 8.2 Roundworms and Segmented Worms

8.2 Roundworms and
Segmented Worms
• The Roundworm is the most common type of worm in the sea.
•In fact they are one of the most popular species in the world.
•Their scientific name is nematode.
•The nematode species are extremely difficult to tell apart from
each other.
•http://www.youtube.com/watch?v=tp-O3LME3OU
Environment of Roundworms
• Small round worms live in sand and mud
• Most worms are found in the moist
substrate of the intertidal zone
Roundworm movement
• To move the roundworm whips the back
half of its body around
• They are able to move through tiny spaces
between sand grains
• Some worms can actually swim thirough
the water
• The motor skills are located in the top of
the head called the, ganglia.
Roundworm appearance
• Roundworms are very very small
• Different sexes
• They are characterized by a cylindrical
body shape
• Fertilization is internal
• Development is external.
• Males and females differ in size and shape
Roundworm body
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Feed on organic debris
Have one way digestive track
No circulatory or respiratory system
Respiratory gases and cellular wastes
pass through its skin
Segmented worms
• The earth is the most common worm on
the planet
• The body of a segmented worm is divided
into parts
• They are called segmented worms or
annelids
The Sandworm
• Live in muddy sands in the intertidal zones
and subtidal zones
• They prey on tiny invertebrates and they
search for organic debris
• Some live inside tubes
• They have hair like bristles called setae
• They have a nervous system to coordinate
the movements of the body
Sandworm continued
• They breathe through their skin like
earthworms
• Carbon dioxide diffuses from the inside of
the body to the outer environment
• Nutrients and respiratory gases are
transported through the body via the
closed circulatory system
• They also have a well-developed excretory
system
Blood worm
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The bloodworm is a polychaete
Has an open circulatory system
They also borrow in the sand
Small and have a thread like appearance
The leech
• This segmented worm has no bristles
• Also called Hirudinea
• Some are free-living and some attach to
hosts
• They have sharp teeth located at the front
of its body
• It secretes a chemical called hirudin to
prevent the host’s blood from clotting
THE END/Citations
Thomas F. Greene. Marine Science. Brooklyn, New York:
Amsco School Publications, 2004.
Wlanier. “A Marine Nematode Roundworm.” August 25,
2006. <http://www.youtube.com/watch?v=tpO3LME3OU>