flatworms , roundworms , and rotifers

Modern Biology: Chapter 34

1

Flatworms, Roundworms, and Rotifers

Chapter 34688-700

http://www.microscopyu.com/moviegallery/pondscum/index.htmlhttp://my.hrw.com/index.jsp

http://www.microscopyu.com/moviegallery/pondscum/index.html

http://my.hrw.com/index.jsp


2

Objectives 34.1

• Summarize the distinguishing characteristics of flatworms

• Describe the anatomy of a planarian

• Compare free-living and parasitic flatworms

• Diagram the life cycle of a fluke

• Describe the life cycle of a tapeworm


3

P. Platyhelminthesflat worms

The P. Platyhelminthes includes organisms called flatworms. Their bodies develop from three germ layers and are more complex than those of sponges, cnidarians, and ctenophores. Flatworms have bilaterally symmetrical bodies, with dorsal and ventral surfaces, right and left sides and anterior and posterior ends.


4

Structure and Function of Flatworms

• Simple• Bilaterally symmetry• Flat body• Has 3 germ layers• Acoelomates• Gas exchange in skin

(diffusion)

• Cephalization• Free living• Parasites (on or

inside animals)• Only one opening

(mouth and anus)• Freshwater or marine


5

Structure and Function of Flatworms

• 20000 species, 4 classes

1. c. Turbellarira

2. c. Trematoda

3. c. Monagenea

4. c. Cestoda


6

1. c. TurbellariraA. Digestion and Excretion in

Planarians (Dugesia) • 4500 species, Salt water and fresh water

- scavengers of decaying plants and animals, small organisms

Pharynx (throat) muscular tube that ingests food and sends food to the gastrovascular cavity diffuses to other parts of the body

Use flame cells (look like flickering candle flames) along with excretory tubules to remove excess water from hypotonic environments


7

1. c. TurbellariraB. Neural control in Planarians

• More complex than cnidarians

• Cerebral ganglia- simple brain, two clusters of nerve cells at the anterior end

• Sensory cells transmit to nerves

• Eyespot- near the cerebral ganglia, can sense the intensity and direction of light

• Can also respond to touch, water currents and chemical in the environment


8

1. c. TurbellariraC. Reproduction in Planarians

• Hermaphrodites

• Sexual reproduction- they simultaneously fetilize each other

• Eggs are in a capsules and stick to rocks (3wks to hatch)

• Can also reproduce asexually (summer)

• The worm will split in two- fission

• Worm can regenerate tail


9


10


11


12

c. Trematoda and c. Monagenea

• Parasitic flukes (leaf-shaped flatworms)

• Parasite

• Endoparasites- live inside organism (blood, intestines, lungs, liver, other organs)

• Exctoparasites- external surfaces (fish and frogs)


13


14


structure of flukes• Anterior suckers and ventral sucker• Simple nervous system• Tegument- outer covering made up of proteins

and carbohydrates that is a defense mechanism

• Protects against digestive enzymes


15


Reproduction and life cycle flukes• Hermaphroditic• Fertilized eggs are store in uterus• May release tens of thousands at one time• Have more than one host


16


17

Schistosoma• Primary host- adult parasite gets its

nourishment, sexual reproduction occurs (humans blood vessels)

• Excreted in wastes fresh water system• Becomes a ciliated larva and will attach a snail

will mature and develop a tail burrow into humans in water

• If eggs don’t leave---- can be fatal• 200million people world widehttp://www.dpd.cdc.gov/DPDx/HTML/Opisthorchiasis.asp?body=Frames/M-R/Opisthorchiasis/body_Opisthorchiasis_page1.htm

http://www.dpd.cdc.gov/DPDx/HTML/Opisthorchiasis.asp?body=Frames/M-R/Opisthorchiasis/body_Opisthorchiasis_page1.htm

http://www.dpd.cdc.gov/DPDx/HTML/Opisthorchiasis.asp?body=Frames/M-R/Opisthorchiasis/body_Opisthorchiasis_page1.htm


18

Schistosoma


19

c. Cestoda

• 5000 species of tapeworms

• Intestines of almost all vertebrates

• Eating raw or undercooked food containing eggs or larvae

• May cause digestion problems, weight loss, lack of energy, anemia, decrees in red blood cells


20


21

c. Cestoda- Structure of Tapeworm

• Also have tegument• Scolex- hooks and suckers to host• Proglottids- long series of body sections• Similar nervous/ excretory system to other

flatworms • Lack eyespots/ other light sensing organs• No mouth, gastrovascular cavity, digestive

organs• Get nutrients by absorbing directly from host

digestive track


22

c. Cestoda- Reproduction and life cycle of

Tapeworm• Hermaphrodites

• 1000000 or more eggs in the proglottid

Tanenia saginatus-

Has two host (human and cow)

Cysts- dormant larvae


23

34.2 Objectives

• Describe the body plan of a nematode

• Outline the relationship between humans and parasitic roundworms

• Describe the anatomy of a rotifer


24

P. Nematoda and P. Rotifera

• Members of the phyla Nematoda and rotifera have bilaterally symmetrical bodies that contain a fluid-filled space. This space holds the internal organs and serves as a storage area for eggs and sperm. It also supports the body and provides a structure against which the muscles can contract.


25

P. Nematoda (roundworms)

• 15000 knows species, estimated 500,000• Long slender bodies that taper at ends• Pseudocoelomates• 1mm to 120 cm• Have a complete digestive tract (mouth-gut –

anus)• Separate sexes• Fresh and salt water, land • Can be parasites of plants and animals• http://www.microscopyu.com/moviegallery/pondscum/nematode/ind

ex.html

http://www.microscopyu.com/moviegallery/pondscum/nematode/index.html

http://www.microscopyu.com/moviegallery/pondscum/nematode/index.html


26

Ascaris• Live in pig, horse, humans intestines• Feed on food from host• Can block hosts intestines• 30cm long (1ft)• 200,000 eggs every day, leave body in feces• Can live in soil for years• Contaminated food and water• Larvae bore into bloodstream lungs and throat

to intestines • Colonoscopy Demonstrating a Moving Worm

http://www.youtube.com/watch?v=HOaZCkA8Zvk




27

Phylum NematodaAscaris worms


28


29


30

Hookworms

• Parasite (tropical and subtropical regions)• Mouth has cutting plates hook on intestinal

wall• Can cause anemia• Can cause slow mental development in

children• Larva live in soil boring through host’s

feet travel to intestines • Infect 1 billion people a year

http://www.hsu.com/images/parasite/hookworms.jpg


31

Trichinella

• Infect human, pigs and other mammals

• Eating undercooked meat

• Live in walls of host intestines

• Larvae are in cysts

• Causes Trichinosis, muscle pain and stiffness

• Cook and freeze at high temps to kill worms


32

Other Parasitic roundworms

pinworm, Enterobius

• Most common 50% in some areas• Not serious • 5-10mm, look like threads• Live in lower region of intestines/ anus• At night female exists and lays eggs• Person scratches during sleep can be passed

on to other persons• Eggs must be ingested and will hatch in intestine


33

Other Parasitic roundworms

Filarial worms-

• Infect over 250 million in tropical countries

• Live in lymphatic system

• 100mm or 4in

• Enter blood passed by mosquitoes

• Causes swollen limbs and the skin hardens and thickens elephantiasis

Toxocara or T. cati- heart worms of dogs and cats


34


35

P. Rotifera- rotifers

• Pseudocoelomates• 1750 species• Transparent• Free-living in fresh water , Can live without water

long periods• 100 to 500 um – males smaller • Multicellular and specialized organs• Cilia around mouth • Parthenogenesis- unfertilized eggs develop into

adult females other produce 2 types of eggs, one is the sperm that will fertilize egg

http://www.cartage.org.lb/en/themes/Sciences/Zoology/Biologicaldiverstity/AnimalsI/rotifer.gif


36

Ascaris Dissection

• http://www.youtube.com/watch?v=_ybbnPj0t9Y&feature=PlayList&p=E0DC6AAA94AFE60F&playnext_from=PL&playnext=1&index=8


37

flatworms , roundworms , and rotifers

Documents