Protostome General Structures & Platyhelminthes (flatworms)

Three germ/tissue layers

Triploblast

This tripoblast tissue type has “NO” body cavity between the gut and outer wall

Acoelomates ( ex: flatworm)

This tripoblast tissue type has “partially” lined body cavity with mesoderm

Pseudocoelomates (ex: Nematode)

This tripoblast tissue type has body cavity “Completely” lined with mesoderm

Coelomates (ex: Earthworm)

Concentration of sense organs, nervous control, etc are located at the anterior end of the body

Cephalization

Benefits of Cephalization

Good for animals that move with the same end of the body forward

• Better motor control

• Better sensory

• Better coordination

Fluid held under pressure in a closed body compartment that function as a skeleton

Hydrostatic Skeletons

Specialized excretory cells that regulate osmotic pressure and maintain ionic balance in organism (removing waste)

Flame Cells (Protonephridia)

This group of protostome contains:

• Triploblastic acoelomates

• Hydrostatic skeleton

• Bilateral symmetry

• Incomplete digestive tract

• Monoecious (containing both male and female reproductive organs)

Platyhelminthes - Flatworms

Platyhelminthes contains the following group

• Turbellaria

• Trematoda

• Cestoda

This Platyhelminthes group has the following:

• Free living flatworms

• Move using ciliated epidermis & muscle contractions

• Found in water & terrestrial

• Carnivorous

• Use chemoreception to find prey

Turbellaria

Know Turbellaria anatomy (Eyespot, Flame cell, Pharynx)

Study the diagram

Know Turbellaria anatomy (Auricle, Gastrovascular cavity, pharyngeal cavity)

Study the diagram

This Platyhelminthes group has the following:

• Parasitic Flukes

• Glands, penetration glands, hooks and suckers (parasitic lifestyle)

• Complex, hermaphroditic reproductive system

Trematoda (The Flukes)

Know Trematoda Anatomy (Oral sucker, Ventral Sucker)

Study the image

Know Trematoda Anatomy (Uterus, Gastrovascular cavity, Excretory pore)

Study the image

Liver Fluke Life Cycle

Study the image:

• Sexually reproduce in human liver

• Asexually reproduce in snails

This Platyhelminthes group has the following:

• Mainly adults found as parasites in vertebrates

• No digestive system

• Absorb nutrients directly throughthe host’s intestine

• Covered in microvilli

• Scolex (head region) with hooks and suckers

• No mouth

Cestoda (The tapeworms)

Cestoda: Body segments that contain gonads and mature as they move away from the scolex

Proglottids

This proglottids are filled with eggs or embryos ready for detachment

Gravid

This proglottids are the site of hermaphroditic sexual reproduction

Mature

This proglottids has no functional reproductive organs

Immature

Structure and function of Cestoda

Study Hooks & Suckers and Scolex