FLATWORM
PHYLUM PLATYHELMINTHES
GROUP 3

• Phylum Platyhelminthes includes the flatworms. Platy
means “flat,” like a plate; helminth “worm”.

Characteristics feature
• Invertebrate organism
• Flatworm have soft and unsegmented body
• No body cavity (no specialized respiratory and
circulatory system) also called acoelomate
• Other species have digestive system (incomplete or
absent)
• Most flatworm have gastro-vascular cavity.
• Diffuse CO2 and O2 through the body wall

Characteristics feature
• Primitive nervous system is present (can sense stimuli
and coordinate movement)
• Have excretory organ called nephridium formed by
channels with terminal flame cell which control
excretion and osmoregulation. (Excretetion of
nitrogenous wastes through protonephridial pores or
their mouth)
• Can reproduce Sexually and Asexually
• Most species are hermaphrodites

Characteristics/features
• They are triploblastic, with three germ layers
(multicellular)
• 80 % are parasitic

Habitat
Flatworm are mostly ecto or endoparasitic and a few are free-
living (usually aquatic)

• Flatworms are bilateral symmetrical. It is different from
radially symmetrical animals, like the anemones, which can
be cut anywhere top to bottom to get two similar halves.
• Non-parasitic flatworm respire through their body surface
while parasitic worms are mostly anaerobes.
Body Structure

• In some flatworms, the process of cephalization has
included the development in the head region of light-
sensitive organ called ocelli.
• Have nervous system consists of a head ganglion connected
to nerve cords which are interconnected across the body by
transverse nerve connections
Body Structure

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Diversity
Divided into three classes:
• Tubellaria, Trematoda and Cestoda
• Class Turbellaria includes non-parasitic and aquatic flatworm (marine
flatworms and planarian).
• Class Trematoda, includes parasitic flatworm that live inside the host,
this are commonly called as flukes (fasciola hepatica and sheep liver
fluke).
• Class Cestoda also known as tapeworms. All tapeworms are internal
parasites.

• Free-living flatworm usually are predators or scavenger
• Have an extended tube-like pharynx out of their mouth
which release digestive enzymes
• In contrast, a parasitic flatworm have a hook or suckers that
attaches to the host’s intestine, and then absorbs the host’s
digested food through body wall.
Feeding

Support and Movement
• Flatworm have a hydrostatic skeleton
• Some flatworms movement is controlled by longitudinal,
circular and oblique layers of muscles.
• Others move along slime trails by beating of epidermal cilia.

• Flatworms reproduce sexually by having both a male and female
part. The majority of sexual reproduction is through cross-
fertilization (where fusion of male and female gametes from
different individual ).
• Asexually through: Fragmentation and regeneration or budding
Reproduction
Video

Protection
• A tough outer layer that protects parasitic flatworm against the
host digestive and immune system
• Free-living forms secrete a protective mucus.
• Have cuticle which protects their body

4 Classes of Flatworms
1. Marine flatworms
2. Planarians
3. Flukes
4. Tapeworms

Marine Flatworm
• Some of the most fascinating creature in the world’s
oceans
• Found in coral reefs
• They are usually brightly colored in black, pinks,
blues, reds, green, and yellow
• Their bright coloring advertises their toxicity to
predators
• Generally carnivorous. They prefer to eat
invertebrates that cannot easily to move, such as sea
squirts, mussels or oysters.

Marine Flatworm
• Marine flatworms are hermaphroditic.
• Life span of marine flatworms is
generally between three weeks to three to
four months long, depending on the
species.
Video

Planarian
• Widely distributed, mostly free-living flatworms
of the class Turbellaria
• They are typically found under rockes and debris
in stream, ponds, and springs.
• Body is elongated, is soft and leaf-shaped. The
spade-shaped head has two eyes. The length is
usually 3 to 15 mm (0.1 to 0.6 inches); some
grow about 1 foot long.
• Most are carnivorous night feeders.
Eyes

Reproduction of Planarian
• They are hermaphrodite. In some species,
the organism in the cocoon divides into two
parts, each of which develops into a complete
individual. New individuals, called buds,
form at tail end of others and may remain
attached to the parents for some time.
• They are remarkable for their ability to
regenerate parts, often they are used
experimentally to study the process of
regeneration.

Fluke
• Class Trematode commonly knows as flukes
or blood fluke.
• Range in size from about 5 mm (0.2 in)
• Commonly parasitize fish, frogs, and turtles;
also invertebrates such as mollusks and
crustacean
• Some are external parasites (ectoparasites)
and endoparasites
• Most are flattened and leaflike or ribbonlike,
some are stout and circular in cross section.

Fluke
• the body is solid and filled with spongy
connective tissue (mesenchyme) that
surround all the body organs.
• Occur in most types of vertebrates;
three species attack humans: urinary
blood fluke, the intestinal blood fluke,
and the oriental blood fluke

Fluke
• Almost flukes make both eggs and sperm.
Blood flukes have separate sexes, and the
adult females and males mate with each
other. Flukes with a direct life cycle use only
sexual reproduction. While indirect life cycle
use asexual and sexual reproduction.

• Also called as class cesteda. They are distinctly
different
• There are two subclasses, Cestodaria and
Eucestoda
• They can grow to long 5 meters long
• They not only eat food by the hots; thye alos
produce wastes and obstruct the alimentary
canal.
• The common types of tapeworms are beef and
pork tapeworms which proven to be dangerous to
human beings.
Tapeworm

Reproduction of Tapeworm
• Tapeworms are also hermaphrodite, each proglottid includes both male
and female gonads and generates both sperm and eggs.
• Can reproduce sexually, either through self-fertilization or cross-
fertilization with another tapeworm
• Can reproduce asexually, breaking off proglottid segments at the end
of the trunk.

• Tapeworms generally do not move around
much but they are capable of having muscular
undulation.
• They use distinguishing feature, the scolex,
which attaches firmly to the host’s intestine
wall. The tip of scolex is equipped with a
rectable hook-bearing rostellum which acts
like disc with teeth to hold onto the intestinal
wall.
• They will just hang on to the intestinal wall,
absorbing food through their skin via diffusion
Attachment

Effects on Humans
Worldwide, endoparasite such as fluke and tapeworms causes
disease of hundreds of million of people and countless
domesticated animals such as sheep, goats, dogs etc. and wild
animals.
Video

Video
• Through their large surface compared to their volume they can
exchange gases like carbon dioxide, oxygen and ammonia across
bodies. Flatworms can adapt to many conditions, which makes them
able to adapt to an enormous variety of habitats.
• They play important roles for healthy streams, ponds, and lakes.
• They also provide food for animals, like dragonflies, when they are
young.
Importance of the organism

Video
FLATWORMQUIZ
1&2. WHAT IS THE SCIENTIFIC NAME OF FLATWORM? ALSO GIVE THE MEANING OF
THE WORD.
3. THE EXCRETORY ORGAN OF FLATWORM FORMED BY CHANNELS WITH TERMINAL
FLAME CELL.
4. HINT: HABITAT. FLATWORM ARE MOSTLY______ AND FEW ARE _______.
5. FLATWORM STRUCTURE IS ______ WHICH IS DIFFERENT FROM ANIMALS LIKE
ANEMONES.
6&7. WHAT NON-PARASITIC AND PARASITIC USE TO TAKE IN THEIR FOODS?
8. FLATWORM ARE CAPABLE OF REPRODUCING ________ AND _______.
9. THEY HAVE NO ______ BECAUSE OF THIS THEY ARE CALLED_________.
PART 2
ENUMERATE THE THREE CLASSES AND INDICATE THE DIFFERENT TYPES OF
FLATWORM IN EACH CLASSES.