Part 2 Phylum Nematoda, Annelida, and Selected Human Parasites

1. Phylum Nematoda
• Ascaris
– Either male or female
• Female – Longer, fatter, straight
• Male – Shorter, thinner, sharp curve at posterior end
– Mouth – At anterior end; three lips
– The Anus is at the posterior end
– Outer Cuticle
– Intestine – Flat, ribbon like-tube that extends straight
from mouth to anus
• Food enters through Mouth, goes through Intestine (while
nutrients are absorbed) and leave out Anus

2. Phylum Nematoda
• One-way; no mix of food and waste
– On inside of Cuticle are opposite each other are
two Lateral Lines
• Can be hard to see
• Join together and terminate at end of excretory pore
• Function as osmoregulatory devices
– All other tubes are reproductive structures
– Female – Have Y shaped structure at anterior end
• Uterus (arms of Y), leading to Vagina (base of Y), and
finally to Genital Pore

3. Phylum Nematoda
– Uterus gradually changes into thin Oviducts and finally into
very fine Ovaries (no destinctions between them)
» Eggs are formed in Ovaries
• Travel through Oviducts to Uterus
• Leave Uterus through Vagina and exit through Genital
Pore
– Male – Tubes start out thickest near posterior end
• Largest tube is Seminal Vesicle attached to Ejaculatory
Duct (where sperm exits)
• Following tube away from Seminal Vesicle leads to thin
Ductus Deferens, and tiny Testis

4. Phylum Nematoda
– No surface distinction (besides size) between them
– Sperm are formed in Testis, travel through Ductus Deferens to
Seminal Vesicle and leave worm’s body by Ejaculatory Duct
• Curve at posterior end of male serves to grasp female
in mating
• Two hair-like Spicules near Ejaculatory Duct
– Aid in transferring sperm into Genital Pore of Female

5. Atlas Ascaris 7.97

6. Atlas Ascaris 7.98

7. Atlas Ascaris 7.99

8. Atlas Ascaris 7.100 & .101

9. Atlas Ascaris 7.102

10. Atlas Ascaris 7.103

11. Ascaris

12. Ascaris Male

13. Ascaris Female

14. Necator 1

15. Necator 2

16. Thrichinella Eggs

17. Atlas Trichinella 7.105
2 is
muscle

18. Phylum Annelida
• Class Polychaeta
– Neanthes
• Sandworm
• Segmentated body
• Parapodia – Little flipper-like structures along side of
sandworm
– Appendages used in swimming and crawling
• Anterior end has first segment called the Prostomium
– Contains its Mouth and small tentacles, eyes, and palps (lip-
like structures)

19. Phylum Annelida
• Anus - At posterior end of sandworm; end of digestive
tract
– The tubeworms secrete a protective outer
covering (tube) and live within it
• Often only part of tubeworm ever seen is tentacles on
Prostomium that are extruded from tube
– Tentacles serve as net to catch food

20. Phylum Annelida
• Class Oligochaeta
– Earthworms
• Inhabitants of underground
• Eat dirt (food and plant debris)
• Till soil (mixing it and aerating it)
– Clitellum – Wide rather smooth band found towards
anterior end
• During reproduction Clitellum secretes mucus layer over
Eggs
– This mucus layer (with Eggs underneath) slides up and off
anterior end
» This creates a Coccoon that shelters the Eggs

21. Phylum Annelida
– Earthworm’s body is is divided into series of
segments
• Can be seen externally and internally
– First segment found at anterior end is the
Prostomium
– Mouth is found at upper end of Prostomium
– Anus is at the posterior end
– Cuticle – Non-living layer; composes worm’s
surface
• Covers body wall that consists of Circular and
Longitudinal Muscles

22. Phylum Annelida
– Ventral surface is covered with series of bristle-like
Setae that aid the worm in motion
– Septae divide segments internally
– Each segment has its own Nephridia (excretory
system)
• Responsible for maintaining osmoreguation in worm
– Too small and delicate to see
• Closely resemble nephron in human kidney
– Coelom – Space between body wall and internal
organs
– At anterior end of worm are reproductive organs
– Three pairs of large white ovals in segments 9-13 are
six Seminal Vesicles
• Enclose Testes that produce sperm

23. Phylum Annelida
• Ductus Deferens carries sperm from Testes to segment
15 where it exits the body
• Ovaries are on segment sides of segment 13; tiny,
white, round
• Posterior to Ovaries are Egg Funnels
– Narrow down into Oviduct in segment 14
» Carries eggs outside worm’s body
• When worms mate their ventral surfaces are contact
– Sperm travels through Ductus Deferens and travel in minute
external grooves that lead anteriorly to Seminal Vesicles of
other worm

24. Phylum Annelida
» Seminal Vesicles are in segments 9-10
» Hold sperm from other worm
• When ready to reproduce, earthworm releases worms
from segment 15
– Eggs are within Mucus Layer secreted by Clitellum
– Will pass seminal receptacles when released and pick up
sperm
– Mucus Layer with now fertilized eggs continues to move up
the worm where it eventually reaches the Prostomium
– Released from worm as the egg coccoon

25. Phylum Annelida
– Just posterior to mouth will be very hard and
muscular Pharynx
• Sucks food into digestive tract
– Beyond Pharynx is long, thin-walled Esophagus
• Partially covered by Seminal Vesicles
– Next digestive organ is Crop
• Usually dark in color; functions as soft roundish storage
bag for food
– Posterior to crop is a lighter colored round Gizzard
• Hard and muscular
• Functions to grind up material that the worm ingested

26. Phylum Annelida
– The Intestine connects the Gizzard to the Anus
• Enzymes convert large pieces of food into usable
molecules that can be absorbed by the worm
• A fold that hangs down into the lumen (space) of
intestine increases surface area of intestine (called the
Typhlosole)
• Undigested food waste is eliminated from worm’s body
through Anus

27. Phylum Annelida
– Ventral Nerve Cord & Ventral Blood Vessel are
visible on ventral side of intestine
• V.N.C. leads anteriorly to “Brain”
– Small bit of shapeless tissue wrapped around anterior end of
Pharynx
– Ventral and Dorsal Blood Vessels lead to anterior
end of worm
• Here they connect to 5 tubular Hearts (dark in color)
that are wrapped around the Esophagus and function
to pump the blood throughout the worm’s body

28. Phylum Annelida
• Class Hirudinea
– Leeches
• Flattened worm-like animals that have an anterior and
posterior sucker
– Used to attach the leech to their host
• Have a mouth containing chitinous teeth that scrape
the skin of their hosts allowing the leech to feed on the
host’s blood
– Inject anesthetic (numbing agent) and anticoagulant (stops
blood clotting) to feed unnoticed
– Have been used for bloodletting (rid people of bad
blood)

29. Atlas Earthworm 7.87

30. Atlas Earthworm 7.88

31. Atlas Earthworm 7.89

32. Atlas Earthworm 7.90 & 7.91

33. Atlas Earthworm 7.92 & 7.93

34. Atlas Earthworm 7.94

35. Lumbricus (1)

36. Lumbricus (2)

37. Earthworm (Segmented Worm)
Lumbricus

38. Earthworm Model (1)

39. Earthworm Model (2)

40. Atlas Leech 7.95

41. Atlas Leech 7.96

42. Leech

43. Atlas Nereis 7.83

44. Atlas Nereis 7.84

45. Nereis

46. Selected Human Parasites
• Parasite – Organism that feeds on its living
host, sometimes rendering harm but usually
not causing the host’s death
• Definitive Host – Where the sexually mature
(adult) parasite lives
• Alternate Host – Where the larval stages of
the parasite live

47. Selected Human Parasites
• Phylum Platyhelminthes
– Clonorchis/Opisthorchis

48. Selected Human Parasites
• Adult liver fluke attaches to human bile ducts and feeds
on lining
• Eggs shed into bile, transport through digestive tract
(DT), exit through fecal matter
• Fecal matter travels into bodies of fresh water
• Snails (A.H.) eat eggs
– Eggs develop and swimming life stage is released into water
where it burrows into muscles of fish (encysts)
• Humans eat improperly cooked fish and liberate the
encysted parasite

49. Selected Human Parasites
• Parasite migrates through DT until it finds bile duct
– Here it attaches, feeds, and reproduces
• Avg human infested with 20-200 flukes per person
– Can cause liver damage

50. Selected Human Parasites
– Fasciola

51. Selected Human Parasites
• Sheep liver fluke
• Life cycle similar to Chlonorchis
• Snails release swimming life stage into water where it
encysts on aquatic vegetation
– Can also encyst in open water without burrowing into
something
• Humans ingest infested vegetation or water
– Acquire parasite

52. Selected Human Parasites
– Schistosoma Mansoni

53. Selected Human Parasites
• Blood fluke Adults live in portal veins of large intestines
• Eggs released into large intestine; shed in feces
– Hatch in water and swimming larvae penetrate tissue of fresh
water snails
• Snails release other stage of swimming larvae into water
• Humans in infested water are targeted by the larvae
– They burrow through skin into a vessel
– They then circulate into the blood stream until reach veins in
large intestine
» There they settle and begin feeding
• Damage caused predominantly by eggs that don’t make it
from the vein into the large intestine

54. Selected Human Parasites
• These eggs circulate in vessels
– Eventually become lodged in organs
» Treated as foreign bodies and isolated by scar tissue
» This scar tissue inhibits proper organ function

55. Selected Human Parasites
• Taenia

56. Selected Human Parasites
• Tapeworms
• Adults live attached to intestinal wall
– Absorb nutrients rom food across their surface
• Mature Proglottid shed with feces
• Cows, pigs, or fish eat Proglottids
– Eggs then are released into animal’s DT
– There eggs develop into mature larvae and encyst in animal’s
muscles

57. Selected Human Parasites
• Humans acquire by eating poorly cooked meat
– Cooking meat to temperature of 56 C or more OR freezing to -
5 C for at least 1 week kills encysted larvae
• Damage to humans from adult parasite includes loss of
energy, cramps, and diarrhea
• Severe medical conditions ensue when humans ingest
Proglottids (usually from pigs)
– Eggs then encyst in human tissues
» Results in scarring that hinders proper organ function
» Scarring is permanent and untreatable

58. Selected Human Parasites
• Ascaris
– Pig roundworm
– Adults live in intestine
• Absorb food that passes through the intestines
– Eggs are passed out of body with feces
• Can be ingested by eating dirty object
• Hatch in intestine and larvae migrate through intestinal
wall to vein
• Vein will carry larvae to lungs
• Larvae burrow out of burrow and climb up bronchi to
trachae to epiglottis where swallowed

59. Selected Human Parasites
• Larvae reaches intestine and becomes adult and feeds
– Can cross placenta and infect fetus
• Damage from heavy build up of worms in intestine, also
migration of larvae (lung infections & bleeding)

60. Selected Human Parasites
• Enterobius
– Pinworm
– Adults live in colon; migrate to anus to mate & lay
eggs
• Males die after mating; females after egg laying
– Eggs cause anus to itch
• Scratching gets them on hands; high chance of
reinfection
– Damage is sleeping problems; intestinal
discomfort

61. Selected Human Parasites
• Necator
– Hookworm
– Adults live in intestines feeding blood
– Eggs shed in fetus
– Larvae survive in soil for several weeks
• Infect human by burrowing into human skin (feet)
– Migrate to blood vessel, carried to lungs, crawl up trachae and
swallowed into digestive tract

62. Selected Human Parasites
• Trichinella
– Circumboreal; humans are a dead road for this
parasite
– Adults live in intestines
• Males die after mating; females after egg laying
– Eggs give rise to larvae that migrate through
circulatory system; settle and encyst in skeletal
muscle
– Humans acquire from uncooked meat