Platyhelminthes (flat worm) Platyhelminthes They are a phylum of - - PowerPoint PPT Presentation

Platyhelminthes (flat worm)

Platyhelminthes

• They are a phylum of relatively simple bilateral,

unsegmented, soft-bodied invertebrates.

Platyhelminthes

Breathing:

• All Platyhelminthes breathe using their entire
• body. Being flat, oxygen diffuses quickly across

the skin and to all parts of the body, so they don't need a blood circulatory or respiratory system.

Platyhelminthes

• There are more than 20,000 species of

Platyhelminthes. 3 main types of Platyhelminthes:

• Turbellaria
• Trematoda (flukes).
• Cestoda (Tapeworms)

Turbellaria

• free-swimming mostly freshwater flatworms
• They are mostly nocturnal and live in shaded

humid locations.

• There are about 4,500 species, which range

from 24 inches to 0.039 inches.

Turbellaria

• Reproduction:
• they reproduce mostly sexually, and

sometimes asexually.

• All turbellarians are hermaphrodites.

Turbellaria

Feeding:

• Most are carnivores, eating tiny aquatic

invertebrates such as rotifers, small crustaceans and other worms

Turbellaria

• Moving:
• Many Turbellarians move by moving their

muscles or cilia in an undulating motion

• sliding over mucus, helps them get form leaf to

leaf

• Swim

http://www.youtube.com/watch? v=zCH37KI_R_E#t=47

Turbellaria

• Sensing:
• Many species of Turbellaria have light sensitive

spots on their front end (these are called ocelli), and some have small flaps sticking out of the side of their heads.

Trematoda

• They are parasitic flatworms.
• Most trematodes have a complex life cycle with

at least two hosts.

• The primary host, where the flukes sexually

reproduce, is a vertebrate.

• The intermediate host, which is the agent of

dispersal, is usually a snail.

• http://www.youtube.com/watch?

v=r7okJ6wHYLA

Trematoda

Reproduction:

• Practically the entire interior is occupied by the

reproductive system; the organism is capable of producing huge numbers of offspring.

• They are hermaphrodites and reproduce both

sexually and asexually

Trematoda

• Movement:
• They have tail-like structures, cilia, for moving

and finding molluscs

Trematoda

Eating:

• The mouth is located at the forward end of the

animal, and opens into a muscular, pumping pharynx

• Adult flukes eat blood cells,

mucus, and body cells

Cestoda (tape worms)

• Humans are subject to parasitism by several

species of tapeworms if they eat underprepared meat such as pork , beef, and fish. Or if they live in, or eat food prepared in, conditions of poor hygiene.

What is the range of size for tapeworms?

They range from 0.5 in. to 100 ft.

Cestoda

• Feeding:

Each of the independent segments is able to absorb the digested food from the host's gut, by diffusion and active transport. Their waste products are released back into the gut the same way.

Cestoda

• Reproduction:
• They are hermaphrodites.
• They do not reproduce asexually, only sexually.

Cestoda

Moving:

• Tapeworms can move around by crawling or
• squirming. They usually come from feces and

as they move around they release eggs that will later hatch into larvae or be eaten by fleas