Chapter 10: Phylum Platyhelminthes

Phylogeny of platyzoa

• tripblostic

• spiral cleavage

• mouth formed from blastopore

Phylum Platyhelminthes has what type of gut

Acoelomate

Phylum Platyhelminthes symmetry

bilateral

Phylum Platyhelminthes is _________ flattened

Dorsoventrally

Platyheminthes has a _______ cavity with one opening

gastrovascular

Platyhelminthes has a _____ Embryo

Triploblastic (ectoderm, mesoderm, endoderm)

Platyhelminthes does not have a ______ system

Hemal (blood)

Platyhelminthes does not have a circulatory system and relies on ______ for gas exchange

diffusion

Parenchyma

(mesoderm) composed of tissue filling

space between epidermis (ectoderm) and gastrovascular

cavity (endoderm)

Platyhelminthes has ____ organ systems

true

nervous system is ______ shaped with large ________ at the head

ladder , cerebral ganglia

most have 2 major _______

nerve chords

Reproductive systems are highly _____

developed

some species have high

fecundity ( produce lots of babies at once)

most species are ________ (have male and female parts)

hermaphroditic

no ________ proposed for phylum

synapomorphy

Four classes of flatworms:

Turbellaria (free living flat worm)

Cestoda (tape worm)

Trematoda (flukes)

Monogenea ( monogeneans)

Class Turbellaria

• mostly marine, some freshwater

• few terrestrial in damp areas

• few are parasitic

• benthic

  • 5mm-50cm

Turbellaria Black spot disease

Ichthyophaga

Turbellaria feeding

• most are predators or scavengers

• eat protozoans, small molluscs, crustaceans, insects, other

  worms

  • juvenile eat algae

Turbellaria digenstion

• pharynx lead to Gastrovascular cavity

• mouth position mid-ventral to anterior

• pharyngeal glands

• Protrusible and retractable pharynx

Pharyngeal glands produce

mucus and digestive enzymes

Turbellaria epidermis

• ciliated cells (vental) (facilitate movement)

• specialized secretory cells

• Rhabdites

• mucous gland cells

  • dual gland adhesive organs

Rhabdites

rod shaped vesicles inside epidermal cells

mucous gland cells

secrete mucous

dual gland adhesive organs

• viscid glands

• anchor cells

• releasing gland

viscid gland

secrete adhesive (allows to anchor)

anchor cells

allows worm to attach

releasing gland

removes adhesive

Muscle

muscle- longitudinal and circular (allows for movement)

what is in between the dorsal and ventral muscle layers

parachymal tissue

Osmoregulation and excretion

Metabolic wastes voided by diffusion

Water and some ammonia removed via

osmoregulatory tubules

(protonephridia)

have beating flagella draw fluids into tubule

Flame cells

Turbellaria Sexual Reproduction

Monoecious with paired female and male reproductive tracts

Each reproductive tract has an independent

gonopore

Some species engage in

reciprocal sperm transfer

Turbellaria Other species engage in

traumatic insemination

traumatic insemination

One worms pierces body of the other with its

hypodermic penis (or penises)`

Parasitism is a type of

symbiotic relationship`

one host

direct lifestyle

more than one host (typically an invertebrate

and a vertebrate)

Indirect lifecycle

Host in which parasite undergoes

development, but not maturity

Intermediate host

Host in which parasite undergoes sexual

maturity

Definitive host

Classes Trematoda, Monogenea, Cestoda Integument

Syncytial integument

Syncytial integument

a multinucleated skin (cells not

fully enclosed by cell

membrane) lacking cilia and

rhabdites

This tegument unites

these classes in the

clade

Neodermata

(parasitic)

Class Trematoda: Subclass

Digenea

Class Trematoda morphology

• anterior oral sucker for attatchment

• acetabullum

• Complex reproductive system

  • Two-branched gastrovascular cavity

acetabullum

ventral sucker

Complex reproductive system

- Single ovary

- Pair of testes

- Coiled uterus

Subclass Digenea: Generalized Life Cycle

Egg- miracidium-sporocyst-redia-cercaria

Subclass Digenea: liver fluke,

Clonorchis sinensis

Chlonorchis sinensis lifecycle

infect snail, infect fish, then infect human

Disease associated with

Chlonorchis sinensis

Can cause inflammation,

abdominal pain, nausea, diarrhea

• Associated with cancer in

prolonged chronic infections

Subclass Digenea: Blood Flukes

• Schistosoma spp. Dioecious

Sexual dimorphism

Life Cycle of Schistosoma spp

snail- human

• Each egg has a spine, can cause

tissue damage

• Eggs in blood become lodged in liver

or other tissues

• Eggs can puncture intestinal wall

• Disease associated with immune

response to eggs and tissue damage

Schistosomiasis

Schistosomiasis

Dysentery, anemia, swollen liver

and spleen, dwarfism, brain damage

About 200 million people

infected in Africa,South

America, the West Indies, Middle

East, and Asia…77 countries

“swimmer’s itch”

Schistosome dermatitis

cercariae of a species whose

normal hosts are birds penetrate human skin

Class Monogenea

• Monogenetic

Mostly ectoparasitic, few endoparasitic spp

Infect aquatic animals, typically fish

monogenetic

one host, direct life cycle `

Monogenea posterior attachment organ, may

have suckers and or hooks

Opisthaptor

Class Cestoda General biology

Tapeworms have long, flat,

ribbon-like bodies

Most species have

at least two hosts:

- Intermediate host: invertebrate

- Definitive host: vertebrate

Class Cestoda Morphology

proglottids

Scolex

No mouth or digestive system

scolex

holdfast structure with suckers and hooks

proglottids

reproductive units

Cestoda Integument covered with

microtriches

microtriches

projections than

increase the surface area for

absorption

(nutrients absorbed by integument)

Cestoda Reproduction

• Posterior proglottids

break off when gravid

• Gravid proglottids, eggs

shed in the feces

Each proglottid produces

about 50,000 eggs

Beef Tapeworm

Taenia saginata

Taenia saginata Lifecycle

cows - humans

Beef tapeworms were

once marketed as a

weight-loss product

(most do not cause tissue damage)

Diseases associated with tapeworms

Pork tapeworm Taenia solium

-from eating under cooked pork

-can cause death and can infect the brain