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“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

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“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: