Transcript V Platyhelminthes and Nematoda PPT

Unit 4 - Phylums
Platyhelminthes and Nematoda
Flatworms and Roundworms
Phylum Platyhelminthes
• Largest group of acoelomate (no body cavity)
worms
• Flatworms with middle tissue layer- mesoderm
• Tissues organized into organs
• Bilaterally symmetrical and flat
• Cells lie close to exterior enabling efficient
diffusion of oxygen and carbon dioxide
• Highly branched gastrovascular cavity runs close
to all tissues giving cells ready access to food
• No respiratory or circulatory systems
Coelom – Body Cavity
• The coelom usually performs multiple
functions, including one or more of the
following:
Provides room for organ development
Surfaces for diffusion of gases, nutrients,
and wastes
Storage
Hydrostatic support
Phylum Platyhelmithes
• Flatworms
– Liver Flukes, Planaria and tapeworms
– Marine flatworms
– Characteristics:
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Ribbon-like bodies
Bilateral symmetry
Branched digestive system
No skeleton
Asexual (fission); Hermaphrodites (sexual)
Free movement
Skin breathing
Phylum Platyhelminthes
• Class Turbellaria
– Most free-living; marine
• Dugesia- Freshwater planarians
– Digestion- Nutrients absorbed by
intestinal wall and waste goes out
through mouth
• Muscular pharynx comes out of
central mouth to feed
Phylum Platyhelminthes
• Reproduction- Mostly asexual by attaching
posterior end to stationary object and pulling
into two
• Hermaphrodites can reproduce sexually
• Nervous system: Brain, two nerve cords, and
light-sensitive eye spots
• Water balance- Water continually enters by
osmosis
• Flame cells with cilia draw water to the outside
Phylum Platyhelminthes
• Marine flatworm
Phylum Platyhelminthes
Planarian
Phylum Platyhelminthes
• Many parasitic
– Endoparasite- internal
– Ectoparasite- external
• Class Cestoidea
• Subclass Eucestoda- Parasitic flatworms
(tapeworms)
– Suckers and hooks on scolex (head) attach to
walls of intestines and food absorbed from
host’s intestines directly through the
tapeworm’s skin
Phylum Platyhelminthes
• String of rectangular body sections
(proglottids)
• Each proglottid is a reproductive unit
• Added continually through life
• May grow up to 12 m (40 ft.) long
Phylum Platyhelminthes
• Most occur in vertebrates
• Dozen types in humans
• Taenia saginata- Beef tapeworm
– Live in cow muscles in cysts
– High temp. kills larvae
– Subclass Cestodaria
• Body not subdidvided into proglottids
• Larvae in crustaceans; adults in fish
Scolex Examples
Phylum Platyhelmithes
Proglottid – reproductive structure
Phylum Platyhelminthes
• Largest flatworm class, Trematoda
– Parasitic worms called flukes
– Endoparasites or ectoparasites
• Subclass Aspidogastrea
(Aspidobothrea)- Endoparasite of
mollusks
• Subclass Digenea- Endoparasites of
vertebrates
Phylum Platyhelminthes
• Tegument- thick protective covering
prevents them from being digested
• Take nourishment directly from hosts
• Use suckers to attach and the muscular
pharynx to suck nourishment from host’s
body fluids
Phylum Platyhelminthes
• Complex life cycles involve more than one host
• Ex: Schistosoma- Responsible for
schistosomiasis
• From contaminated water
• Larvae bore into host skin into blood vessels of
intestines
• Block vessels causing bleeding and damage to
liver
• Snail is intermediate host
Phylum Platyhelminthes
• Class Monogenea –
– Monogenetic flukes
– One life cycle in one host
– Mostly ectoparasites on vertebrates
Phylum Platyhelminthes
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Liver fluke
Phylum Nematoda
• Roundworms- have a pseudocoelom (body
cavity between endoderm & mesoderm)
– Fluid movement serves as circulatory and gas
exchange system
– Fluid also distributes nutrients to cells from
digestive system
Phylum Nematoda
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Long, cylindrical bodies
Majority microscopic and free-living
One-way digestive system
Thick, flexible epidermis protects and
gives shape
• Layer of muscle underneath pulls at
epidermis and pseudocoelem for whip-like
movement
Phylum Nematoda
• Roundworms
– Ascaris, Trichinella and hookworms
– Characteristics:
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Flattened bodies
Bilateral symmetry
Many are parasites
Fluid-filled body cavity called a pseudocoelem
Digestive tube
No skeleton
Sexual reproduction (Internal fertilization)
– Sperm is amoeboid
• Free movement
• Skin breathing
Phylum Nematoda
• Class Secernentea (Phasmidea)- Phasmids (sensory
structures) in tail
– Ascaris, Enterobius, Rhabditis, Turbutrix, Necator,
and Wuchereria
• Class Adenophorea (Aphasmidia)- No phasmids
– Dioctophyme, Trichinella, Trichuris
• 50 species are parasitic
• Plant parasites feed on living plant cells in all parts of
plant, causing wilting and withering
• 14 species affect humans
– Ex: Enterobius (pinworms), Ascaris lumbricoides,
Trichinella spiralis, Necator (hookworms)
Phylum Nematoda
• Trichinella infects pigs
and causes trichinosis
(serious disease caused by
eating undercooked pork)
• Necator live in warm,
moist soils of the tropics
– Hookworm larvae enter
bloodstream through soles
of feet
Phylum Nematoda
• Ascaris
– Carried in human waste
– After ingestion, eggs hatch
into larvae in intestines
– Larvae bore through blood
vessels, enter blood stream
and then lungs (causes
respiratory distress)
– Larvae may enter
gallbladder or pancreas
causing blockages
– Return to intestines to
mature and mate
– May grow up to 1 ft. in
length
Phylum Nematoda
• Ascaris
• Trichinella
Trichinosis
• Trichinella spiralis is
found in pork
• Trichinosis is a disease
caused by the Trichinella
worm.
– Eggs hatch in the host’s gut
– Symptoms:
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Diarrhea
Fever
Muscle pain
Death
Common Parasitic
Roundworms
• Pinworms- most common
• Heartworms- transmitted to
dogs by mosquitos
• Filarial worms- live in blood
where they block blood
vessels or lymph vessels
causing severe swelling
(Elephantitis)
• Guinea worm- Ingested with
contaminated water
– Cause dracunculiasis
– Only found when exiting skin
– Found in Africa, India and
Pakistan
• Hookworms attach to
the inside of the
digestive tract
• Often found in pets