Flatworms

1
Worms!

• Flatworms
• Roundworms
• Segmented worms

2
Types of Worms

• Flatworms (Phylum Platyhelminthes)
• Class Turbellaria (Planeria)
• Class Trematoda and Monogenea (Flukes)
• Class Cestoda (Tapeworms)
• Roundworms (Phylum Nematoda and Rotifera)
• Ascaris
• Hookworms
• Trichinella
• Pinworms
• Filarial worms
• Segmented worms (Phylum Annelida)
• Class Oligochaeta (Earthworms)
• Class Hirundea (Leeches)

3
Flatworms Phylum Platyhelminthes

• Flatworms are the simplest creatures with
  bilateral symmetery.
• They develop from three germ layers.
• They do not have a hollow body cavity.
• Because they are flat, they can exchange oxygen
  and CO2 with the environment through diffusion.
• They have no circulatory or respiratory systems.
• They have an incomplete digestive system
  consisting of a gut with a single opening.
• Nerves and sensory organs are located at one end.
  This is known as cephalization.
• Many flatworms are parasites, living on or in
  other creatures. Some are not and are found in
  freshwaters, marine, and terrestrial
  environments.

4
Flatworms Phylum Platyhelminthes

• Class Turbellaria
• Includes the Planarians, such as Dugesia species.
• Feed by scavenging bits of decaying plant and
  animal matter.
• Food is ingested through a muscular tube which is
  extended out from the body.
• How do they get ride of excess water?
• Flame cells draw in excess water water is
  transport through tubules and excreted through
  pores.
• What are the cerebral ganglia, and what do they
  do?
• Simple brain respond to stimuli and transmit
  signals to muscles
• Describe two way Planarians reproduce
• Sexually
• Fertilize each other and lay eggs on rocks or
  debris
• Asexually
• Worms splits in two by attaching to solid surface

5
Flatworms Phylum PlatyhelminthesPlanaria
6
Flatworms Phylum Platyhelminthes

• Class Trematoda and Monogenea
• Consists of parasitic flukes.
• They can live in the blood, intestines, lungs,
  liver, or other organs and are called
  endoparasites.
• Ones that live on the outside of their host are
  called ectoparasites.
• How does a fluke stick to its host and what else
  does this structure do?
• Anterior sucker and ventral sucker
• Most flukes are hermaphroditic and have a complex
  life cycle that involves more than one host.
• Once disease caused by flukes includes
  Schistosomiasis which affects more than 200
  million people each year in Asia, Africa, and
  South America.

7
Flatworms Phylum Platyhelminthes
8
Flatworms Phylum Platyhelminthes

• Class Cestoda
• Also known as tapeworms, which can live in the
  intestines of almost all vertebrates.
• At the anterior end is a structure known as the
  scolex. What is its structure and function?
• Has hooks and suckers that enable the worm to
  attach to its host.
• Behind the scolex are the body segments called
  proglottids.
• What happens to these during reproduction?
• They grow in length become fertilized from
  another either from same individual or another
  individual.
• How can a human become infected with a taperworm?
• When they eat undercooked beef

9
Flatworms Phylum PlatyhelminthesTapeworm
10
Roundworms Phylum Nematoda and Rotifera

• Roundworms have bilaterally symmetrical bodies
  and a fluid filled space to store eggs and sperm
  and for support.
• They have a complete digestive system, that is,
  one with two openings, unlike cnidarians,
  ctenophores, and flatworms.
• They have separate sexes. The vast majority are
  free-living on on land and in the water, and are
  parasites of plants and animals.

11
Roundworms Phylum Nematoda and Rotifera

• Ascaris
• Live in intestines of humans as larvae, then move
  to bloodstream and are carried to lungs and
  throat? can block air passages and cause
  bleeding.
• Hookworms
• Go through feet and travel through blood to lungs
  and throat
• If ingested, they will move to intestines and
  develop into adults
• Trichinella
• Live in intestines larvale travel through blood
  stream to muscles and form cysts, causing muscle
  pain and stiffness (trichinosis)
• Pinworms
• Live in intestines tiny white threads in the
  lower intestines females come out at night and
  lay eggs on anus which spreads via scratching.
• Filarial worms
• Elephantitis? infects lymphatic system and is
  spread by mosquito

12
Roundworms Phylum Nematoda Ascaris
13
Roundworms Phylum Nematoda Hookworms
14
Roundworms Phylum Nematoda Trichinella
15
Roundworms Phylum NematodaPinworms
16
Roundworms Phylum NematodaFilarial worms
17
Segmented worms Phylum Annelida

• Feather-duster worms, common earthworms and
  leeches, are all members of this phylum.
• The phylum name means little rings.
• These organisms are bilaterally symmetrical and,
  like mollusks, have a true coelom, a complete
  internal body tube
• What does this structure allow to happen when the
  organism moves?
• It allows the body to contract.
• Most have external bristles called setae.
• All organ systems are well-developed.

18
Segmented worms Phylum Annelida

• Class Oligochaeta
• The most familiar members of this class is the
  earthworm.
• Describe how it moves (and the structures
  involved)
• Thay have a fluid skeleton, and to move forward,
  they squeeze circular muscles of each segment, to
  extend their body.
• They use their rough bristles to grip the surface
  of the ground at the front, then use longitudinal
  muscles to pull their ends up to meet the front
• Complete or incomplete digestive tract? Explain.
• Complete? two openings and one-way
• Open or closed circulatory system? Explain.
• Closed?via two main blood vessels, dorsal and
  ventral
• Oxygen and CO2 diffuse directly through the skin.
• The nervous system consists of a chain of ganglia
  connected by a ventral nerve cord.
• How do earthworms reproduce? Be sure to mention
  any special structures and their functions
• Two press their ventral surfaces together with
  anterior ends pointing in opposite directions
• They are held be setae and clitellum
• Exchange sperm with each other, ideally
  fertilizing each other (they are hermaphodites!)

19
Segmented worms Phylum Annelida- Earthworms
20
Segmented worms Phylum Annelida

• Class Hirudinea
• Consists of about 500 species of leeches.
• They have no setae. At each end is a sucker that
  can attach to surfaces.
• What two things do they secrete when they suck
  blood?
• Anaesthetic
• A substance that prevents blood from clotting

21
Segmented worms Phylum Annelida- Leeches