Flatworms (Platyminthes)

Platyhelminthes are the origin of…

Bilateral Symmetry and Cephalization

Located inside clade _______ which is in Lophotrochozoa

Protosomia

What is a Lophophore?

A feeding appendage with tentacles surrounding mouth

• Platyhelminthes do not have this.

Basic Characteristics of Platyhelminthes

• Live in wet environments (marine, freshwater…)

• Dorsally flat

• Triploblastic Acoelmates

• Incomplete Gut

Body Systems that are not in Platyhelminthes

NO Respiratory, Circulatory, and Skeletal Systems

Sensing Organs

• Statocysts (detects vibration)

• Ocelli (light sensing eyespots)

Nervous System

• Paired Anterior Ganglia (simple brains)

• Longitudinal Nerve Cords

Reproduction Systems

They are monoecious

• Fragmentation

• Penis-fencing

• Internal Fertilization

Excretory System

Use “Flame Cells” like kidneys

• Cillia that moves waste.

Platyhelminthes includes 4 classes:

• Turbellaria (free-living)

• Trematoda (flukes)

• Mongenea (monogenetic flukes)

• Cestoda (tapeworms)

New Guinea Flatworm

Class and Characteristic?

Class: Turbellaria

• They are invasive

• Top predator to snails

Triclad Gut vs. Polyclad Gut

Turbellarian “Branched Guts”

• Triclad Gut: Three Main Braches

• Polyclad Gut: Many Branches

Genus of Turbellarians

Planarians

• “Freshwater Turbellarians”

Planarian Anatomy

• Have muscle of Body wall and Pharynx

• Ciliated Epidermis w/ Rhadibites (for mobility)

• Adhesive Organ (2 viscid & 1 releasing glands)

Trematoda vs Turbellaria

Trematoda is similar to Turbellaria

• but they include features for parasitism (oral suckers)

Geneses of Class Trematoda

• Clonorchis (human liver fluke)

• Fasciola (sheep liver fluke)

• Schistoma (human blood fluke)

Clonorchis Life Cycle

1. Flukes eggs are passed through feces in water.

2. Snail consumes eggs. They then leave to hatch.

3. Once hatched they penetrate fish

4. Human eats raw fish, Flukes then inhabits their liver.

5. Adult flukes are then passed in feces

Fasciola Life Cycle

1. Eggs passed through feces in freshwater

2. Embryos are released and invade snails

3. Once developed, they leave snail and swim to grass.

4. Grazing animals ingest the cysts

5. Flukes emerge inside host. Migrates to liver to develop.

Schistoma Life Cycle

1. Sporocysts develop in snail

2. Cercaria is released in water

3. Penetrates human skin in vascular system

How is Class Monogea “Monogenetic flukes”?

Only latch onto ONE host

• typically fish

Simple Class Monogea Life Cycle

• Egg

• Free-living Larva (oncomidium)

• Adult Parasite w/ Opishaptor

Class Cestoda Anatomy

• Proglottids - repeating segments (w/ male & female organs)

• Scolex - head used to infect host

• They have NO gut

Genus of Cestoda

Taenia

• Beef Tapeworm

Taenia Life Cycle

1. Eaten and passed by human (in raw meat) - Adult

2. Gets into grass and eaten by cow - Shelled Larva

3. Cow becomes host - Cysticerus Juvenile

4. Cow is then slaughtered for consumption

Inside Lophophotrocozoa is clade _______. has Phylum Nemeterea

Kryptochozoa

Phylum Nemertea (Ribbon Worms) Characteristics

• Eucolemates w/ Complete Gut

• Eversible Proboscis: tube to catch prey (Rhynocoel)

• 4 lobed brain paired w/ Longitudinal Trunks

• Similar to Platyhelminthes