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Po
rife
ra
Cn
ida
ria
Cte
no
ph
ora
Ph
oro
nid
a
Ec
top
roc
ta
Bra
ch
iop
od
a
Ec
hin
od
erm
ata
Ch
ord
ata
Pla
tyh
elm
inth
es
Mo
llu
sca
An
ne
lid
a
Art
hro
po
da
Ro
tife
ra
Ne
me
rte
a
Nem
ato
da
“Radiata” Deuterostomia Protostomia
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
Phylum: Nematoda
pseudocoelomate
Kingdom: Animalia
Phylum: Nemata
•non-segmented, worms
•tapered at both ends
•bilateral symmetry
•most common soil inhabitant
•15,000 parasitic species
•covered in thick, tough, protective cuticle
•cuticle is a syncitial epidermis
•molt several times during lifespan
•triploblastic
•pseudocoelomate- 1st group to evolve a body
cavity
Kingdom: Animalia
Phylum: Nematoda (formerly Aschelminthes)
pseudocoelomate- coelom
partially lined with mesoderm
Advantages of a Body Cavity
•fluids can function as circulatory system
•forms a “hydrostatic skeleton”
•organs can function without being deformed
by body movement
•food movement not controlled by locomotion
of animal making digestion and waste removal
more efficient
•complete digestive system
•one-way digestion (mouth and anus)
•tube within a tube body plan
•nervous system
•sensory structures and ganglia at head
•ventral and dorsal nerve cords
•Reproduction: sexual
•most have separate males
and females (dioecious)
•reproductive organs
in body cavity
Kingdom: Animalia
Phylum: Nematoda
cross-section
•locomotion
•longitudinal muscles under epidermis
•no circular muscles
•can undulate only side-to-side (whip-like
motion)
•“hydrostatic skeleton” aids in movement
•excretory system
•waste moved via fluid in body cavity
•may have excretory ducts/pores as well as
gland cells for waste removal
•no respiratory or circulatory system
•gas exchange by diffusion
•food and nutrients distributed via fluid in body
cavity
Phylum: Nematoda
Phylum: Nematoda
Genus: Ascaris
Ascaris lumbricoides
• parasite of humans that causes ascariasis
• largest intestinal roundworm (15-35 cm)
• can block intestine, bile duct, pancreatic duct
• in tropical, sub-tropical areas with poor
sanitation
• caused by accidental ingestion of fertilized
eggs
• most common human helminth infection
worldwide
• infection easily treated
Hookworms
hookworms attached to intestinal mucosa
Phylum: Nematoda
•adults attach themselves to intestinal mucosa
•feed off of blood
•can cause severe anemia
•humans contract when larval form bores through
skin after contact with contaminated soil
•treatment: freezing if still on skin, anti-helminthic
drugs
Phylum: Nematoda
Pinworms
•geographically found everywhere
•common in school age children, spread by
oral-fecal route
•live in large intestine
•eggs ingested hatch in small intestine, then
migrate to large intestine to mature
•eggs can survive 2-3 weeks outside human
body
•treatment: anti-helminthic drugs kill larvae
and adult, not eggs
Beware the 10 second rule!
Phylum: Nematoda
Trichinella spiralis causes trichinosis
•larvae encysted in striated muscle
•cysts formed by host immune response
•larvae passed to another organism
when undercooked meat is eaten
•in new host, cyst digested in stomach
releasing worm, then adult develops in
intestine
•adult worms deposit larvae in lymph vessels
and wall of intestine
•larvae migrate throughout body
•larvae that make it to muscle encyst in their
new host
Phylum: Nematoda
Trichinella spiralis causes trichinosis
•humans can get from eating
undercooked pork
•most damage of infection is when 1/2
billion larvae bore through the body at
once
•severe cramping, fever, anemia,
weakness
•some victims may have permanent
muscular damage; others may die
•prevention: thoroughly cook pork, freeze
pork
•rare in developed countries
Phylum: Nematoda
Trichinella spiralis
causes trichinosis
Filaria worms
Phylum: Nematoda
•significant in human disease
•intermediate host (vector) is arthropod
•definitive host is a vertebrate
•cause of...
•elephantiasis in humans
•heartworm in dogs
filaria worms cause the disease
elephantiasis (lymphatic filariasis)
•intermediate host =
mosquito
•definitive host = dog
•fatal to dog
Phylum: Nematoda
Filaria worm causes heartworm in dogs
Dirofilaria immitis
Filaria worms:
Wuchereria bancrofti
causes the disease
elephantiasis
Phylum: Nematoda
•found in tropical and subtropical areas
•spread by bite of certain mosquitoes
•adult worms live in lymphatic system
•block lymph flow
•causes fluid accumulation, swelling, especially
in the lower extremities
Po
rife
ra
Cn
ida
ria
Cte
no
ph
ora
Ph
oro
nid
a
Ec
top
roc
ta
Bra
ch
iop
od
a
Ec
hin
od
erm
ata
Ch
ord
ata
Pla
tyh
elm
inth
es
Mo
llu
sca
An
ne
lid
a
Art
hro
po
da
Ro
tife
ra
Ne
me
rte
a
Ne
ma
tod
a
“Radiata” Deuterostomia Protostomia
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
Phylum: Rotifera
pseudocoelomate
•usually free-living, moist soil or aquatic
•corona
•double crown of cilia at anterior end
•draw water current into mouth for
feeding & locomotion
•foot
•at posterior end
•when feeding, attaches to surface
•nearby cement gland generates
the adhesive
•mastax
•complicated muscular pharynx
Kingdom: Animalia
Phylum: Rotifera
Kingdom: Animalia
Phylum: Rotifera
•pseudocoelemate
•complete digestive system
•have excretory and reproductive systems
•no circulatory or respiratory system
•reproduction can be sexual or by parthenogenesis
•parthenogenesis- in some species females
produce 2 different kinds of diploid eggs, female
and male, that develop without fertilization to
diploid adults
•in some species, eggs can develop as dwarf
males that cannot even feed themselves, only
survive long enough to produce sperm to fertilize
females (sexual dimorphism- sexes take on 2
different forms)
Symmetry: bilateral
Segmentation: none
Mesoderm present: yes, triploblastic, has only longitudinal muscles
Type of body cavity: pseudocoelomate; fluid filled pseudocoel enclosed by cuticle forms hydrostatic skeleton
Ciliated larva: have larva that molt (shed cuticle as they grow)
Protostome: no? (this is under debate among scientists, newer molecular evidence may revise this)
Cleavage/cells: determinate
Nervous system: present; 2 nerve cords (dorsal & ventral)
Digestive system: complete one-way system (mouth & anus); pharynx usually muscular; some heterotrophs but mostly
parasites
Excretory system: yes, excretory ducts and pores to eliminate waste, some have gland cells and/or canal systems, too
Reproductive system: sexes usually separate (dioecious); male reproductive tract opens to rectum forming common exit
called the cloaca; female reproductive tract opening separate from digestive tract
Circulatory system: none
Members: hookworms, pinworms, common roundworm, trichinella
Habitat: moist soil; the most numerous inhabitant of the soil; also found in aquatic environment; some parasites
Relationship to other phyla: N/A
The Table for Nematoda:
(If nothing is listed for a category, assume it is the same as for Nematoda.)
Reproductive system: sexual or by some by parthenogenesis (produce diploid eggs that grow to diploid
adult without fertilization); some exhibit sexual dimorphism producing degenerate dwarf males that live only
long enough to fertilize eggs
Members: rotifers
Habitat: freshwater and marine environments, moist soil
Relationship to other phyla: cuticle suggests rotifers are close relatives of roundworms
The Table for Rotifera: