1. Biology 11 – Kingdom Animalia Study of the Primitive Worms
Phylum Platyhelminthes: Flatworms
Phylum Nematoda: Roundworms
BIOL 316
Phylum Platyhelminthes

2. Phylum Platyhelminthes – the Flatworms
The Planarians
The Flukes
The Tapeworms

3. Importance of the Flatworms to Evolution
Bilateral body plan – left side mirror image of right
Cephalization – development of the head
sense organs and nerves concentrated in head region
Centralization of nervous system:
Nerve cord accompanies cephalization and bilateral symmetry.
Advanced muscle tissue present;
Primitive excretory system
allows removal of metabolic wastes

5. Flatworms (Phylum Platyhelminthes)
Definition:
Flatworms are soft, flattened worms that have tissues and internal organ systems.
They are the simplest animals to have 3 embryonic germ layers, bilateral symmetry, and cephalization
Flatworms are acoelomates, meaning “without a coelom”
 coelom = a fluid-filled body cavity that is lined with mesoderm
 mesoderm = middle germ layer that gives rise to muscles, circulatory, reproductive, and excretory systems

6. Phylum Platyhelminthes Characteristics
Bilateral symmetry; anterior and posterior ends.
Body flattened
Well-developed epidermis
No internal body cavity other than digestive tube (acoelomate)
Parenchyma (connective tissue) fills space between organs.
Incomplete digestive system
Still one opening
This critter eats and poops out of its mouth – mmmm, pass the popcorn

7. Cross Section of a Flatworm

8. Advantage of Being Flat
Surface area to volume ratio is important for organisms.
Many substances enter and leave through body surface.
Faster absorption and release of wastes
3mm
Volume = 3 x 3 x 3 = 27mm2
Area = 6(3 x 3) = 54mm3
9mm
3mm
1mm
Volume = 9 x 3 x 1 = 27mm2
Area = 2(9 x 1) + 2(3 x 1) + 2(3x9) = 78mm3

9. Nutrition and Digestion
Typical digestive system includes a mouth, a pharynx, and an intestine.
Parasitic Tapeworms and Flukes lack a digestive system
Parasitic flatworms, such as the Tapeworm absorb molecules from host.
Free living flatworms (Planarians) are carnivorous; suck prey into pharynx with mouth.
Undigested food goes out mouth. Yes, folks, they eat and excrete out the same hole 

10. Flatworm Respiratory, Circulatory, and Excretory System
Lack circulatory, respiratory, and excretory systems.
Flatworms rely on diffusion to transport oxygen and nutrients throughout the body, to remove CO2 and other wastes
Some flatworms have flame cells – specialized cells that remove excess water and metabolic wastes

11. Nervous System and Sense Organs
Have a nerve-net.
Most have more complex system.
Cerebral ganglion = primitive brain coordinates impulses.
“Ladder” system carries impulses throughout body
Many sense organs present
Eyespots
Chemoreceptors, touch sensors and rheoreceptors (sense direction) also common

12. Note: Free-living vs. Parasitic
Free-living (eg Planarians) have well developed digestive and nervous systems to seek-out and process food
Parasitic Tapeworms – rely on host’s digestive system to process food, which absorb. No need for advancement of nervous system – not needed.

15. Reproduction – in Free-living Flatworms such as Planarians
May reproduce sexually or asexually
Asexual:
Binary fission – split in two
Sexual:
Both sexes present in same flatworm (hermaphrodites).
Fertilization internal, eggs produced
Embryos emerge as juveniles resembling adults.

16. Reproduction in theTapeworm!
Lack digestive system
Sucker and hooks on anterior end for attachment
Neck produces new segments
Called proglottids
Each proglottid contains male and female gonads
Reproductive output high
Many proglottids per worm
Many eggs per proglottid

17. Groups of Flatworms Turbellarians Free-living, e.g. planarian
Flukes (Trematoda)
Parasites
Tapeworms (Cestoda)

20. Tapeworm - Life Cycle

21. Flukes -- Life Cycle of a Liver Fluke

22. The Coelom or Body Cavity Advances

23. Another Look at the Coelom

24. Phylum Nematoda (Roundworms)
Definition:
Roundworms are unsegmented worms that have pseudocoeloms and digestive systems with two openings – a mouth and an anus
Pseudocoelom = “false coelom”
Is a body cavity between the endoderm and mesoderm tissues, partially lined with mesoderm tissue

26. Form and Function in Roundworms
Feeding: free-living carnivores; or eat algae, fungi, decaying organic matter
Respiration: gases diffuse through body walls
Circulation: no internal transport system  diffusion
Excretion: metabolic wastes diffuse through body walls

27. Form and Function in Roundworms
Response: ganglia from the head and run through length of body; sense organs to detect chemicals of other organisms
Movement: muscles and fluid of the pseudocoelom function as a hydrostatic skeleton; allows movement (swimming or pushing through soil)
Reproduction: sexual reproduction; internal fertilization, were male deposits sperm inside the female’s reproductive tract

28. Roundworm Ecological Roles
Omnivores that catch and eat algae, fungi, decaying matter
Recyclers
Parasites of Plants – eg. The Golden Nematode attacks potato crops, causing severe devastation
Parasites of animals

29. Ascaris – Parasitic Roundworm of Pigs and Humans

30. Unfortunately, they can Grow quite Big!

32. Parasites: Your Pet's Enemies Tiny parasites that pose a gigantic threat
  Heart worms inside the dog's heart, can grow to a length of 14". What they do: Restrict blood flow and cause organ damage. Symptoms include coughing. labored breathing, heart failure. Untreated, heart worm disease can kill a dog. Death may occur within 72 hours. How they spread: Transmitted by over 70 species of mosquitoes. Virtually all dogs are at risk.
Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice.

33. Adult roundworms live in the dog's small intestine
Adult roundworms live in the dog's small intestine. What they do: Cause diarrhea, vomiting, stunted growth, rough coat, bloated belly. How they spread: Almost all puppies get roundworms from their mothers. Dogs can also pick up roundworms from the soil. Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice.

34. Enlarged hook worm mouth showing 'teeth'
Enlarged hook worm mouth showing 'teeth'. What they do: Attach to the dog's intestinal lining, leaving bleeding internal wounds. Cause blood loss, anemia, and diarrhea. As few as 100 hook worms can kill a puppy. How they spread: Eggs pass through the feces of an infected dog into the soil where they are easily swallowed or can penetrate through a dog's feet. Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice.

35. Symptoms:
Larvae digested enter bloodstream and burrow into organs, causing absolutely horrendous pain and in some cases death.

36. Filarial (threadlike worms) are nematodes that may block the passage of Fluids in the Body
Disease: Elephantitis
The disease is caused by parasitic worms, including Wuchereria bancrofti, Brugia malayi, and B. timori, all transmitted by mosquitoes. Lymphatic filariasis currently affects 120 million people worldwide, and 40 million
Blocks Lymphatic nodes which drain fluid to and from the blood.
Tropics, Africa and Asia

37. Phylum Annelida (Earthworms)
Annelida  annellus, meaning “little ring”
Definition:
Annelids are worms with segmented bodies. They have a true coelom that is lined with tissue derived from mesoderm.

39. Body Plan
The body of an annelid is divided into segments separated by septa (singular: septum)
Septum – internal walls between each segment
Most segments contain the same organs (eyes, antennae, sense), while others are specialized
Most segments have bristles called setae

41. Feeding and Digestion
Annelids may be filter feeders or predators (carnivorous)
Annelids use their pharynx (with jaws) to bring food into the esophagus. The food then go into the crop (food storage) and then to the gizzard (food is ground up). Then food is absorbed in the intestine.

43. Circulation Annelids have a closed circulatory system.
Blood is contained in a network of blood vessels
Blood circulates through a dorsal vessel and a ventral vessel, and smaller blood vessels through each segment
Dorsal vessel helps pump blood

45. Respiration Annelids can respire through:
Gills (worms that live in water)
Diffusion through skin (earthworms)

46. Excretion Digestive waste passes out anus
Metabolic waste is filtered out by nephridia

47. Response
Most annelids have a well-developed nervous system with a brain and nerve cords
Other sense organs:
Sense receptors, chemical receptors, sensors that detect gravity

48. Movement Hydrostatic skeleton
Contraction of longitudinal and circular muscles
Annelids can burrow, use setae, or parapodia (paddlelike appendages for swimming or crawling)

49. Reproduction Sexual reproduction
May have separate sexes and external fertilization OR
Annelids are hermaphrodites and exchange sperm with another worm
Two worms attach, exchange sperm, and store it in sacs
A clitellum (a thick band) secretes a mucus ring where the egg and sperm are released and fertilization takes place inside this ring
The ring falls off the worm and forms a cocoon, where the eggs will hatch

50. Ewwwwwwwwwwwwwwwwwwwwwwwww!
Ah, but they are sooooooo in love, don’t you think?

51. Class Oligochaeta Earthworms
Streamlined bodies, few setae, live in soil or water

52. Class Hirudinea Leeches
External parasites that suck blood and body fluids of host
Medical uses: reduce swelling, helps blood clotting
Have suckers at one or both ends for attachment. Produce a chemical in saliva called HIRUDIN, which is an anti-coagulant

54. Leech Anatomy 101
Mmmm – lunch! 

55. Leeches Used in Medicine
Successful reattachment of severed ear, as blood continued to flow and carry nutrients to the damaged region

56. Class Polychaeta Sandworms, blood worms
Marine annelids with parapodia (paired paddlelike appendages)

57. Ecology of Annelids
Annelids are important for our environment because they:
Burrow through the soil, aerating and mixing it
Decompose plant matter
Food source (for birds, moles, toads, snakes, etc.)