Phylum: Phylum: PlatyhelminthesPlatyhelminthesClass: TurbellariaClass: Turbellaria

By By Mr. “I wish I could regenerate” Mr. “I wish I could regenerate”

ChapmanChapman

PlatyhelminthesPlatyhelminthesClass Turbellaria – Are free-living flatworms, are

scavengers that can be found in 3 different habitats:

1. Freshwater species like planaria

PlanariansPlanariansPlanarians are frequently used to Planarians are frequently used to

demonstrate the regenerative capabilities demonstrate the regenerative capabilities of lower invertebrate animals. of lower invertebrate animals.

If cut in half, two Planaria will result. If the If cut in half, two Planaria will result. If the head is split lengthwise, two heads will head is split lengthwise, two heads will result after healing is complete.result after healing is complete.

Not all Planarians will look the same. There are hundreds of species and they all vary in color, shape and size. Planarians live on land in tropical rainforests and in freshwater lakes, rivers, and streams.

Eyespot

Planarian StructurePlanarian Structure Planaria’s eyespots allow Planaria’s eyespots allow

them to detect light but them to detect light but they cannot focus like they cannot focus like your eyes. your eyes.

The The ganglionganglion, their , their primitive brain is visible primitive brain is visible along the inside margins along the inside margins of each eyespot, giving of each eyespot, giving Planarians a “cross-eyed” Planarians a “cross-eyed” appearance.appearance.

Planarian StructurePlanarian Structure Two long nerves that extend Two long nerves that extend

from the Planarian’s head to from the Planarian’s head to posterior end fuse at the posterior end fuse at the anterior end to form the anterior end to form the ganglion. ganglion.

Having sensory organs Having sensory organs concentrated at the anterior concentrated at the anterior end of an animal is called end of an animal is called cephalization. cephalization.

Cephalus means head. Cephalus means head.

Planarian StructurePlanarian Structure Therefore flatworms are the first animals to have a head. Therefore flatworms are the first animals to have a head. Consequently if they have a head, they then have a right and left Consequently if they have a head, they then have a right and left

side. Cephalization then, leads to a new kind of organization among side. Cephalization then, leads to a new kind of organization among animals called bilateral symmetry. animals called bilateral symmetry.

Animals with bilateral symmetry have two sides. Bi = two and Animals with bilateral symmetry have two sides. Bi = two and lateral = sides.lateral = sides.

PlatyhelminthesPlatyhelminthes

2. Marine flatworms like sea slugs

There is also a There is also a diversity of marine diversity of marine flatworms. Many are flatworms. Many are brightly colored brightly colored warning (Apsomatic) warning (Apsomatic) fish that they taste fish that they taste bad.bad.

Others are cryptically colored allowing them to camouflage with their surroundings. Marine flatworms, like Planaria, are in the class Turbellaria.

Examples of TurbellariansExamples of Turbellarians 3. Terrestrial

species like ribbon worms

Scavengers Mistaken for

earthworms

The End