1. PHYLUM PLATYHELMINTHES
FLATWORMS

3. What’s new? 1. TRIPOBLASTIC: have 3 germ layers:
Ectoderm: outside – skin and nervous system
Endoderm: inside – lines internal organs, vessels
(ie: guts, arteries)
*Mesoderm: middle – everything else, esp. muscle

4. 2. Acoelomate:
=NO BODY CAVITY (NO COELOM)
= NO ORGAN SYSTEMS

6. -have a “brain” in the anterior end
BILATERAL SYMMETRY:
-have a “brain” in the anterior end
-if you cut a flatworm in half (along the mid-dorsal line
from anterior to posterior) you will have two equal
pieces. This only works one way.
ACOELOMATE
mid dorsal cut

7. - have a better nervous system - called a NERVE LADDER
-gives them better discrimination (they can tell left from right).
ACOELOMATE

9. SENSORY APPENDAGES (ANTERIOR END): -eyespots -auricles
ACOELOMATE
auricles

10. Hunters need good sensory skills

11. -incomplete digestive system -GVC (gastrovascular cavity)
-MOUTH but still NO ANUS
-PHARYNX ‘vacuums up food’
-gut is highly branched and transports food to all cells in body
ACOELOMATE

13. -gets rid of nitrogenous wastes & excess water
7. EXCRETORY SYSTEM:
-gets rid of nitrogenous wastes & excess water
-a specialized contractile vacuole
-called “flame cell”
-as it gets filled up, it moves to the edge of the worm, contracts and releases its contents outside the worm
ACOELOMATE

14. -get oxygen as it diffuses across their thin body wall
8. RESPIRATORY SYSTEM:
-NO LUNGS!
-get oxygen as it diffuses across their thin body wall
-that is why they are flat as no cell can be too far from the outside
ACOELOMATE

15. -amazing regeneration ability -cut in half = 2 new identical worms
9. REPRODUCTIVE SYSTEM:
Asexually
-amazing regeneration ability
-cut in half = 2 new identical worms
ACOELOMATE

16. -hermaphrodites (each individual is male & female)
9. REPRODUCTIVE SYSTEM:
Sexually
-hermaphrodites (each individual is male & female)
-all flatworms have eggs and sperm
-to have sex, 2 worms exchange sperm and both have offspring
ACOELOMATE

17. Why is this one so special?

18. PENIS FENCING Flatworms are hermaphrodites
When flatworms encounter each other, they engage in a 60 minute ‘dance’ during which they repeatedly strike at each other, both trying to inject their sperm under the skin of the other worm.
The ‘winner’ becomes the male for that encounter, and the ‘loser’ must care for the fertilized eggs.

21. -the larger organisms ate the flatworms
10. PARASITISM:
-when larger, more complex organisms with coeloms evolved, the flatworms became easy prey
-the larger organisms ate the flatworms
-the flatworms took advantage of their flat shape
to hide inside the body cavities.
-they adapted and evolved:
a) hooks and suckers to hold fast
b) a unique tegument (skin layer) to protect them from their hosts defenses.
There are now more species of parasitic flatworms, flukes and tapeworms then there are free living forms.
ACOELOMATE

23. Classification
Class Cestoda
Class Trematoda
Class Turbellaria

24. CLASS
CESTODA
These flatworms have suckers and teeth that grasp the host in the small head. Behind a short neck are repeated parts of the worm, each containing reproductive structures that contain both eggs and sperm, which can pass out through the host's feces, like fluke eggs. These repeated parts are in order, with the oldest parts farthest away from the head of the tapeworm. The pieces give the worm a ribbonlike structure, beneficial for absorbing nutrients from the intestine, where these parasitic tapeworms live
Symptoms             •Diarrhea             •Straining to defecate             •Segments in feces

25. TAPEWORMS are intestinal parasites in vertebrates.
Very simple: no nervous system (no senses or brain), no digestive system, no excretory system, and no muscles.
Has a very well developed reproductive system.
They compete with us for OUR food.

26. TAPEWORMS
Special structures:
1 – body segments = PROGLOTTIDS
2 – SCOLEX with:
a) hooks
b) suckers

30. SCOLEX

31. Tapeworm body

32. TAPEWORMS
How to prevent yourself from getting tapeworm:
1 —cook your meat WELL DONE
2 —TREAT the sewage.

34. Tapeworm coming out of cat: http://www.youtube.com/watch?v=FjBZmEwcd3s
In digestive system:
Gut infestation with tapeworms
Tapeworm coming out of cat:

35. EGGS
Tapeworm cysticercus and egg

40. CLASS
TREMATODA
Classes Trematoda and Monogenea represent the parasitic flukes. These flatworms have similar structures to class Turbellaria but their mouth is at the anterior end. These worms have suckers in the mouth that attach to blood vessels near the intestine. The smaller female fluke fits into a groove on the male, and they are often found attached, a position in which they can copulate freely. The eggs pass out in the host's feces and the larva can infect another organism and assexually divide to reproduce. Often, a fluke life cycle will involve living in more than one host. Many flukes can infect humans, and cause diseases such as schistosomiasis, infecting millions in developing countries.
Symptoms -                  •Jaundice                 •Enlarged Painful Abdomen                 •Bottle Jaw                 •Anemia                 •Poor body condition

41. FLUKES
-Are all parasitic
-Have complex life cycles
-Specialized body parts:
1. Oral Sucker
2. Posterior Sucker
-Many infest humans:
heart flukes
blood flukes
liver flukes
lung flukes
intestinal flukes

43. Life Cycle of a Liver Fluke

44. Liver Flukes Removal of a liver fluke:
Fasciola Hepatica
Removal of a liver fluke:

47. SHEEP WITH A CHRONIC LIVER FLUKE INFECTION
SHEEP: This picture shows a sheep liver with chronic fluke infection, indicated by numerous adult flukes in the enlarged bile ducts and massive fibrosis
SHEEP WITH A CHRONIC LIVER FLUKE INFECTION

48. Blood Flukes
BLOOD FLUKES
Males blue
Females clear

49. BLOOD FLUKES
Males blue
Females clear

50. Blood fluke:

55. Schistoma eggs in bladder

56. CLASS
TURBELLARIA
Class Turbellaria are the nonparasitic, free-living flatworms. These worms have large eyespots and flaps on each side of the head to detect chemicals. These worms live in water, usually on the underside of rocks. They have a highly branched digestive tract, but the one opening, or mouth, is on the ventral surface, rather than in the anterior end. The tube extending from the mouth is used to suck in materials as the worm uses cilia to crawl on the floor of the water.

57. FREE LIVING FLATWORMS
-Are NOT usually parasitic
-predators
-eat meat
-live in oceans, freshwater, and moist places on land (terrestrial)
-Specialized body parts:
1. auricles
2. eyespots
3. pharynx

58. FRESHWATER FLATWORMS Ie: planaria 1. Pharynx 2. Auricle 3. Eye spot
5. Gastrovascular cavity
Ie: planaria

60. FREE LIVING WORMS

62. Life Cycle of a Planaria
Planaria are hermaphrodites (have testes & ovaries)
Sexual Reproduction:
-2 worms each transport their sperm to another planaria
-the gametes join = zygote
-this is shed from the body in a capsule
-weeks later they hatch
Asexual Reproduction:
-planaria detaches its tail and each half regrows the lost parts via regeneration.

63. WATCH PLANARIA MOVING! Planaria:
Regeneration in Planaria (start at 1 min):
Worm inside your face:
Land Planarian in Borneo:

64. Marine flatworms : The marine flatworms (polycladids) are the largest of the free-living flatworms, sometimes reaching lengths of 15 centimeters. Polycladids get their name from their highly branched digestive cavity. These individuals were photographed on a reef near the island of Guam. (Click on either of the pictures above for a larger image).
MARINE FLATWORMS

70. Some Attack Jellyfish & Anemones
Some free living flatworms prey upon cnidarians. Especially their tentacles (with cnidocytes).
-They eat the cnidocytes without firing its toxic stinger.
-Then the cells migrate from the digestive system to the epidermal surface
-The flatworm then uses the cnidocytes (with their nematocysts) to defend itself! Cool!

71. terrestrial FLATWORMS
Hunter:
-kills earthworms
-ruins soil