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
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)
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
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
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
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
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