8 Parasitic Adaptations in Helminths

Dr. PARVISH PANDYA’s presentation

“Parasitic adaptations in Helminths”

A presentation compiled from various sources by

Dr. PARVISH PANDYA,Zoology Dept. Bhavan’s College, Andheri.


Sites from which presentations have been downloaded and later editted. I am indeed thankful to them for their kindness and support :http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.htmlhttp://faculty.pnc.edu/jcamp/parasit/parasit.htmlhttp://www.amnh.org/rose/hope/creatinghope/http://www.biology.eku.edu/SCHUSTER/bio%20141/POWERPOINT%20NOTES/Intro%20to%20Protozoa_files/fullscreen.htmhttp://www.biosci.ohio-state.edu/~zoology/eeob405/http://www.tulane.edu/~wiser/protozoology/pwpt/http://www.iep.water.ca.gov/suisun/photos/wildlife.htmlhttp://www.uta.edu/biology/marshall/2343/http://www.uta.edu/biology/faculty/faculty.htmlhttp://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htmhttp://bio.fsu.edu/http://www.aw-bc.com/http://www.nhm.org/http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/

It is very easy to find mistakes in these presentations…..I request you to kindly rectify them and supply me the modifications needed at [email protected] a lot and have fun in teaching & learning Zoology….

http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.html

http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.html

http://faculty.pnc.edu/jcamp/parasit/parasit.html

http://www.amnh.org/rose/hope/creatinghope/

http://www.biosci.ohio-state.edu/~zoology/eeob405/

http://www.tulane.edu/~wiser/protozoology/pwpt/

http://www.iep.water.ca.gov/suisun/photos/wildlife.html

http://www.uta.edu/biology/marshall/2343/

http://www.uta.edu/biology/faculty/faculty.html

http://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htm

http://bio.fsu.edu/

http://www.aw-bc.com/

http://www.nhm.org/

http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/

mailto:[email protected]


Phylum Platyhelminthes & Aschelminthes = Helminth worms

flatwormsSelected characteristics: Anatomy: thin and flat; digestion - free-living and parasitic forms excretion - protonephridia (flame cells) nervous - 1st CNS;ganglia, 2 ventral nerve

cords, eyespots, auricles


Triploblasts

PseudocoelomatesNematodaRotifera

AcoelomatesPlatyhelminthesGastrotricha?Nemertea?

Coelomates

ProtostomesMollusca OnycophoraAnnelida Nemertea?Arthropoda Bryozoa?Tardigrada

DeuterostomesEchinodermataHemichordataChordata

Deuterostomemouth not from blastopore

Protostomemouth from blastopore


1. Phylum Platyhelminthes: Flatworms are acoelomates with gastrovascular cavities

• There are about 20,000 species of flatworms living in marine, freshwater, and damp terrestrial habitats.– They also include many parasitic species, such as the

flukes and tapeworms.• Flatworms have thin bodies, ranging in size from

the nearly microscopic to tapeworms over 20 m long.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings


Phylum Platyhelminthes

• Flat worms• Triploblastic• Acoelomate• Bilateral symmetry• Hermaphroditic

– Monoecious

• One opening for digestive system

• Ladder nervous system


Flatworms are divided into four classes: TurbellariaMonogeniaTrematodaand Cestoidea



1. Class Turbellaria

• free-living flatworms planarians (Dugesia) highly branched gastrovascular

• cavity pharynx - muscular• opening to gastrovascular cavity


Class Turbellaria

• Eye spots• Ciliated surface• Regenerate if cut in

two


Turbellarian Pharynx

Platyhelminthes• the most primitive bilateral animals?• 80% parasites (derived)• specialization potential• Class Turbellaria


• respiration• many w/symbionts for the O2• increased respiration rate • some deep (5 cm) sediment hunters w/ hemoglobin and symbionts


• Flatworms have an excretory system called protonephridia, consisting of a branching network of dead-end tubules.– These are capped by a

flame bulb with a tuft of cilia that draws water and solutes from the interstitial fluid, through the flame bulb, and into the tubule system.



• Flatworms and other bilaterians are triploblastic, with a middle embryonic tissue layer, mesoderm, which contributes to more complex organs and organs systems and to true muscle tissue.

• While flatworms are structurally more complex than cnidarians or ctenophores, they are simpler than other bilaterans.– Like cnidarians and ctenophores, flatworms have a

gastrovascular cavity with only one opening (and tapeworms lack a digestive system entirely and absorb nutrients across their body surface).

– Unlike other bilaterians, flatworms lack a coelom.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings


• Planarians and other flatworms lack organs specialized for gas exchange and circulation.– Their flat shape places all cells close to the

surrounding water and fine branching of the digestive system distributes food throughout the animal.

– Nitrogenous wastes are removed by diffusion and simple ciliated flame cells help maintain osmotic balance.

Fig. 33.10


Turbellarian GI tracts• increasing complexitymicroturbellariansAcoela

• simple pharynx• no gut cavity

macroturbellariansTricladia (3-branched)

• tubular protrusible pharynxPolycladida (multi-branched) - marine

• 3-brached protrusible pharynx

pharynx plicatus

Protonephridia• excretory• osmorgulatory• flame cells• filtration• selective absorption

Sensory structures• brain (ganglia)• net-like nervous system• variable number of longitudinal

nerve cords• evolutionary trend toward

net reduction• bilateral brain• paired longitudinal nerve cords• “pigment cup” ocelli (no. varies)• strong negative phototaxis• sensory pits -> chemoreception• complex behaviors - learning


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

Acoelomate

Phylum Platyhelminthes: Class Turbellaria

Parenchyma• tissue connecting muscles and gut• large flatworms: mesenchymal cells in an extracellular matrix• small flatworms: matrix minimal or absent• liquid in some some fw forms - hydrostatic skeleton + internal transport• parenchymal cells types• epidermal replacement cells • neoblasts - totipotent, wound healing• fixed parenchymal cells - join cells and tissues• low-resistant pathways for intercellular transport of metabolites


2. Classes Trematoda and Monogenea

• flukes• parasites• many feed with oral suckers and microvilli• oral and ventral suckers used to attach to host• gastrovascular cavity - not branched• hosts: primary-where sexual reproduction of parasite

occurs• intermediate-no sexual reproductive stage of parasite• Examples: Schistosoma mansoni - human blood fluke• Clonorchis sinensis - Chinese liver fluke


Class Trematoda

• Flukes• Parasites• Holdfast devices

– Most

• Complex life cycle• Intermediate host

– Animal with juvenile stage

• Definitive host– Animal with adult stage


• Trematodes parasitize a wide range of hosts, and most species have complex life cycles with alternation of sexual and asexual stages.– Many require an intermediate host in which the

larvae develop before infecting the final hosts (usually a vertebrate) where the adult worm lives.



Fascioloa hepatica

• Sheep liver fluke• Sheep, cattle and man

– Weight loss

• Eat vegetation with metacercaria


Generalized

Fluke



Phylum: Platyhelminthes

Class: Trematoda

Fluke

Fig. 46.6Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings



Life Cycle of the Sheep Liver Fluke


Schistosoma

• Blood flukes• 200 million people• 1 million deaths/year


• The blood flukeSchistosoma infects200 million people,leading to body pains,anemia, and dysentery.



Life Cycle of a Schistosome Fluke


Schistosome

• Cercaria have forked tail


Class Cestoidea

• Tape worms• No digestive system• 40 feet long


3. Class Cestoda

• tapeworms• parasitic• no digestive cavity• body: head = scolex• proglottids = body sections containing male and

female sex organs• Examples: human tapeworms; pigs, cows, and fish

are intermediate hosts• Sushi - tapeworm infestation has risen with the

popularity of this dish• ??Filariasis?


• Tapeworms (class Cestoidea) are also parasitic.– The adults live mostly in

vertebrates, including humans.

• Suckers and hooks on the head or scolex anchor the worm in the digestive tract of the host.

• A long series of proglottids, sacsof sex organs, lie posterior to the scolex.

• Tapeworms absorb food particles from their hosts.


• Mature proglottids, loaded with thousands of eggs, are released from the posterior end of the tapeworm and leave with the host’s feces.– In one type of cycle, tapeworm eggs in

contaminated food or water are ingested by intermediary hosts, such as pigs or cattle.

– The eggs develop into larvae that encyst in the muscles of their host.

– Humans acquire the larvae by eating undercooked meat contaminated with cysts.

– The larvae develop into mature adults within the human.


Platyhelminthes• rhabdoids and rhabdites• some expel rhabdites to ensnare prey and gather detritus• duo-glands (adhesive and releaser glands)

• multi-ciliated cells• pedal waves• muscles• looping



Pork Tapeworm

(Taenia solium)


Scolex


UterusUterusTestesTestes

OvaryOvary

Yolk glandYolk gland

Vas deferensVas deferens

Seminal receptacleSeminal receptacle

Proglottid


Life Cycle

of the

Broad-Fish

Tapeworm

Diphyllobothriumlatum


Aschelminthes? Ecdysozoans?• the molting aschelminths• ecdysone-like steroids• 4 molts during development• multi-layered collagen cuticle• epidermis often syncytial• continue to grow between molts• eutely


Phylum Nematoda

• 12,000 species– 500,000 possible

• Cylindrical body• Only longitudinal

muscles• Noncellular cuticle

with several layers• Pseuodcoelomate• Mouth and anus


• Found everywhere– Soil– Oceans– Polar ice– Hot springs

• Parasites of nearly all plant and animal species!

Nematodes


Musculature and Movement• no circular muscles - no peristalsis • dorsal and ventral longitudinal muscles• innervation – muscle processes extend to nerve cords• high internal pressure 10 x greater than most inverts• rigid cuticle, partially contracted muscles• round• sinusoidal waves


Feeding• 6 muscular lips (often fused to 3)• muscular pharynx moves food and keeps gut lumen open• pharyngeal glands lubricate + enzymes • digestion mainly extracellular• wastes voided by the minute


Respiration and Circulation• diffusion


little host specificity

12 US spp., 2 common

females sluggishmales active


Internal and

External

Features of a

Nematode

Dr. PARVISH PANDYA’s presentationNematode Reproductive Systems


Ascaris lumbricoides

• Roundworm of man• 1.2 billion people in US• Females lay 200,000 eggs a day• Unsanitary habits contaminate ground• Night soil


Dioecious


Life Cycle of Ascaris lumbricoides


Trichinella spiralis• Trichina worm• Pigs, bear, dogs, cats,

rats and man• Trichinosis

– Encysts in muscles


Life Cycle of Trichinella spiralis


Wuchereria bancrofti• Lives in lymphatic

system• Obstruct lymph to

cause swelling– Elephantiasis


Elephantiasis


Life Cycle

of

Wucheria spp.


The End

8 Parasitic Adaptations in Helminths

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