“Radiata”
Metazoa
Ancestral colonial
flagellate
Deuterostomia
Eumetazoa
Protostomia
Bilateria
Phylum: Nematoda
pseudocoelomate
Nematoda
Nemertea
Rotifera
Arthropoda
Annelida
Mollusca
Platyhelminthes
Chordata
Echinodermata
Brachiopoda
Ectoprocta
Phoronida
Ctenophora
Cnidaria
Porifera
Kingdom: Animalia
Phylum: Nematoda (formerly Aschelminthes)
•non-segmented, smooth worms
•tapered at both ends
•bilateral symmetry
•>80,000 species described
•most common soil inhabitant
•15,000 parasitic species
•generally less than 5 cm (some parasitic ones longer)
•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 Evolution of a Body Cavity
•fluids moving within cavity can function as
circulatory system
•fluid in cavity makes body rigid allowing for
muscle driven body movement, 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
Kingdom: Animalia
Phylum: Nematoda (formerly Aschelminthes)
•complete digestive system
•one-way digestion (mouth and anus)
•tube within a tube
•nervous system
•sensory structures and ganglia at head
•nerve ring with ganglia around the pharynx
•ventral and dorsal nerve cords
•reproduction is sexual
•most have separate males and females
(dioecious)
•reproductive organs in body cavity
•females release chemical attractants
Kingdom: Animalia
Phylum:
Nematoda
(formerly
Aschelminthes)
•locomotion
•longitudinal muscles under epidermis
•no circular muscles
•can only undulate side-to-side (whip-like motion)
•no cilia
•“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
Kingdom: Animalia
Phylum: Nematoda (formerly Aschelminthes)
cross-section
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 with anti-helminthic drugs.
Phylum: Nematoda
Hookworms
hookworms attached to intestinal mucosa
•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 here
•common in school age children, spread by oral-fecal route
•adult male 1-3 mm, female 8-13 mm
•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
Phylum: Nematoda
Filaria worms
•significant in human disease
•intermediate host (vector) is arthropod
•definitive host is a vertebrate
•cause of...
•elephantiasis in humans
•heartworm in dogs
Phylum: Nematoda
Filaria worms:
Wuchereria bancrofti
causes the disease
elephantiasis
•found in tropical and subtropical areas
•spread by bite of certain mosquitoes
•adult worms live in lymphatic system
•accumulate to large numbers and block lymph
flow
•causes fluid accumulation, swelling, especially
in the lower extremities
filaria worms cause the disease
elephantiasis
Just FYI:
Phylum: Nematoda
Filaria worm causes heartworm in dogs
•intermediate host = mosquito
•definitive host = dog
•fatal to dog
“Radiata”
Metazoa
Ancestral colonial
flagellate
Deuterostomia
Eumetazoa
Protostomia
Bilateria
Phylum: Rotifera
pseudocoelomate
Nematoda
Nemertea
Rotifera
Arthropoda
Annelida
Mollusca
Platyhelminthes
Chordata
Echinodermata
Brachiopoda
Ectoprocta
Phoronida
Ctenophora
Cnidaria
Porifera
Kingdom: Animalia
Phylum: Rotifera
•microscopic (50µm - 2mm long)
•usually free-living, in moist soil or aquatic environments
•corona
•double crown of cilia at anterior end
•look like rotating wheels when they beat
•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
•seven hard jaw-like structures crush food
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 dimorphismsexes take on 2 different forms)
Kingdom: Animalia
Phylum: Rotifera
cilia beat in opposite
directions to create
current
(cement glands)
The Table for Nematoda:
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 Rotifera:
(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