1 Unit 5.1 Phylum Platyhelminthes. 2 Phylum Platyhelminthes Flat worms Triploblastic – three primary germ layers Acoelomate – no body cavity Bilateral

1

Unit 5.1

Phylum Platyhelminthes

2


• Flat worms• Triploblastic – three primary

germ layers• Acoelomate – no body cavity• Bilateral symmetry• Hermaphroditic

– Monoecious – Having both sperm and egg producing parts

• One opening for digestive system – located ventrally. Food is eaten and excreted through the same tube.


• Paired lateral nerve cords & cerebral ganglion – very simple

• Flame cells – specialized “kidney” cells

• No specialized circulatory or respiratory systems – must be flat so nutrients & oxygen can diffuse throughout the body

3

4

MyxozoaMyxozoaMyxozoaMyxozoa

ArthropodaArthropodaArthropodaArthropoda AnnelidaAnnelidaAnnelidaAnnelida

MolluscaMolluscaMolluscaMollusca

LophophoratesLophophoratesLophophoratesLophophorates

HemichordataHemichordataHemichordataHemichordata

ChordataChordataChordataChordata

Other Other pseudocoelomatespseudocoelomates

Other Other pseudocoelomatespseudocoelomates

NematodaNematodaNematodaNematoda

PoriferaPoriferaPoriferaPorifera

CtenophoraCtenophoraCtenophoraCtenophoraCnidariaCnidariaCnidariaCnidaria

PlacozoaPlacozoaPlacozoaPlacozoa

PlatyhelminthesPlatyhelminthesPlatyhelminthesPlatyhelminthesNemerteaNemerteaNemerteaNemertea

CiliophoraCiliophoraCiliophoraCiliophoraSarcomastigophoraSarcomastigophoraSarcomastigophoraSarcomastigophora

MicrosporaMicrosporaMicrosporaMicrosporaApicomplexaApicomplexaApicomplexaApicomplexa

MesozoaMesozoaMesozoaMesozoa

EchinodermataEchinodermataEchinodermataEchinodermata

CrustaceaCrustaceaCrustaceaCrustaceaChelicerataChelicerataChelicerataChelicerata

UniramiaUniramiaUniramiaUniramia

ProtochordatesProtochordatesProtochordatesProtochordates

5

AcoelomateAcoelomate

EctodermEctodermMesodermMesodermEndodermEndoderm

Coelom – A fluid filled space that is completely surrounded by mesoderm

6

7

Phylum Platyhelminthes: Class Turbellaria

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Acoelomate

8

PseudocoelomatePseudocoelomate



9

CoelomateCoelomate



10

Nervous System

Lateral nerve cordLateral nerve cord

ConnectivesConnectives

AuricleAuricleEye spotEye spot

Cerebral ganglionCerebral ganglion

11

BrainBrain

AuricleAuricle

Cerebral Cerebral ganglionganglion

PairedPairednerve cordsnerve cords

12

Excretory System


13

14

15

Turbellaria


16

17

Class Turbellaria• Eye spots – detect simple

light gradients. • Ciliated skin surface

secretes mucous and aids in movement.

• May be aquatic or terrestrial. Terrestrial species are all nocturnal.

• Most are free-living – not parasites but predators/scavengers.

Class Turbellaria

18

• Planarians have the ability to regenerate new body parts or to generate an entirely new organism from pieces of themselves.

19

20

Class Trematoda

• Flukes• Parasites• Holdfast devices

– Most possess these

• Complex life cycle• Intermediate host

– Animal with juvenile stage

• Definitive host– Animal with adult stage

21

22

Clonorchis sinensis

Oral sucker

Intestine

Uterus

Yolk gland

Testes

Ovary

Seminal recepticle

23

24

Clonorchis sinensis

• Chinese liver fluke• 50 million people infected.• Cirrhosis of liver – liver

tissue is replaced by non-functioning scar tissue that impairs overall liver function

• Diarrhea• Edema – fluid beneath the

skin.• Severe gut pain.

25

26

Fascioloa hepatica

• Sheep liver fluke• Sheep, cattle and

man– Weight loss

• Eat vegetation contaminated with metacercariae – small capsules that house the intermediate stage of the fluke.

27

Life Cycle of the Sheep Liver Fluke


28

Fasciolopsis buski

• Intestinal fluke• 10 million people• Man and pigs• Hemorrhage and

abscesses of small intestine

29

30

Paragonimus westermani

• Lung fluke• Carnivores, pigs,

rodents and man• May be fatal

31

32

33

Schistosoma

• Blood flukes – parasitize mesenteric blood vessels.

• 200 million people infected.• 1 million deaths/year.• Second most deadly

parasite behind malaria.• Males wrap around

females & they exist in pairs throughout adult lives.

34

Life Cycle of a Schistosome FlukeCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Eggs are expelled in urine or feces to fresh water where the larvae pass through an intermediate stage involving a snailhost and then enter through the skin of a passing human host.

35

Schistosoma

• The eggs all have a hook that tears bodily tissues throughout the human host causing more damage as they are passed.

• Larvae have a forked tail that assist them in borrowing through human skin.

Schistosoma

36

37

Swimmers Itch – Related to Blood Fluke

Swimmers Itch

• Need avian hosts to complete their life cycle.

• Humans are “accidentally” infected and develop a rash for around a week.

• Sores develop around burrowing sites but the larvae die within a few hours of entering the skin

38

39

Class Cestoidea

• Tapeworms• No digestive system –

suck in pre-digested nutrients from the intestines of the host that are directly utilized in metabolic processes.

• Can grow up to 100 feet long. Human tapeworms may reach 60 feet in length.

Class Cestoidea

• The scolex, or head, is equipped with suckers designed to anchor the worm to the intestinal wall and to suck in nutrients.

• The proglottids are hermaphroditic segments, each able to detach from the body and produce eggs.

40

Class Cestoidea

• Infections are usually asymptomatic other than lethargy and/or dull abdominal pain.

• The lethargy is due to a lack of nutrients caused by the tapeworms’ feeding. This leads to weight loss.

• People may purposefully infect themselves with tapeworms to lose weight.

41

Scolex

42

43

Proglottid

UterusUterus

TestesTestes

OvaryOvary

Yolk glandYolk gland

Vas deferensVas deferens

Seminal receptacleSeminal receptacle

44


Pork Tapeworm (Taenia solium)

45

Taenia saginata

46

Echinococcus granulosus

• A tapeworm that causes a potentially fatal parasitic disease called hydatid disease.

• Herbivores, and sometimes humans, become the intermediate hosts after ingesting eggs on vegetation.

Echinococcus granulosus• The eggs then hatch into

embryos that lodge in tissues and grow into huge cysts containing thousands of tapeworm larvae.

• When the cysts finally cause the host to die or become easy prey, they are ingested by the scavenger/predator and become adults in their intestinal tracts.

47

48

49

The End

Documents

1 Unit 5.1 Phylum Platyhelminthes. 2 Phylum Platyhelminthes Flat worms Triploblastic – three primary germ layers Acoelomate – no body cavity Bilateral