Platyhelminthes and Nematodes

The Bilateria are characterized by what and it allows for what?

characterized by bilateral symmetry which allows for specialization

What phylum do flatworms belong to?

Platyhelminthes

What are characteristics of Platyhelminthes (flatworms)?

• acelomates

• soft bodied

• 1 mm to many meters

• many parasitic, others free-living

• move by ciliated ventral epithelial cells

• musculoskeletal

Flatworms typically want to move to what type of environment?

To the dark

What is the left most line?

eye spot

What is the middle line?

mouth

What is the right most line?

protruding pharynx

What is the top left(#1)?

testis

What is number 2

oviduct

what is number 3?

sperm duct

What is number 4?

nerve cord (runs along ventral side)

What is number 5?

intestine

What is number 6?

epidermis

What is number 7?

parenchymal muscle

what is number 8?

longitudinal muscles

what is number 9?

circular muscles

flatworms are _____ in most cases

hermaphrodites

What is the arrow pointing to?

Intestine

What is the top arrow pointing to?

anterior cerebral ganglion

What is the bottom arrow pointing to?

Nerve chord

What is the top arrow pointing to?

ovary

What is the bottom arrow pointing to?

Testis

Platyhelminthes have a ____ gut with a ______ ________

blind, ventral opening

What type of digestion do you have if you have a blind gut?

incomplete digestive system

What allows food to be torn into small bits in platyhelminthes?

muscular contractions in the pharynx

True or False: Platyhelminthes have some extracellular digestion

True

What does the phagocytosis?

cells that line the gut

What worm lacks mouths and digestive systems?

Tapeworms (parasitic flatworms)

How do tapeworms get food?

Absorb food directly through body walls and live in the intestines

Platyhelminthes have what two main systems?

Excretory and Osmoregulatory systems

Describe the physical parts of the systems

• network of fine tubules runs through body

• flame cells located on the side branches of tubules

Describe the process of water movement

• internal cilia move water and excretion into tubules

• then removed through pores between epidermal cells

What is the primary function?

water balance

what is the secondary function?

excretion

Most ________ diffuses into ________ and eliminated through _______

metabolic waste, the gut, the mouth

What is the black line pointing to?

excretory canal

What is this an image of?

insides of a platyhelminthe

What is line 1 pointing to?

excretory pore

what are lines 2 and 3 pointing at?

fluid movement

what is the 4th line pointing to?

cilia (in others it can be flagella too)

What is line 5 pointing to?

Nucleus

What is line 6 pointing to?

flame cell

What are the last two lines pointing to?

Tubule cells

Respiration

gas diffuses between cells and the air

What does a simple nervous system consist of?

• anterior cerebral ganglion

• bilateral ventral nerve cords with transverse connections (like ladder rungs)

• eyespot can distinguish light from dark

Characteristics of reproduction in platyhelminthes

• most hermaphroditic with cross fertilization

• many have internal fertilization

• direct and indirect development

• regeneration

What is internal fertilization?

sperm is delivered inside

What is direct development and what type of animals have it?

embryo directly develops into an adult, found in freshwater worms

What is indirect development and what animals have it?

has a larval stage, occurs usually in marine animals

What are the two major groups of platyhelminthes?

turbellaria and neodermata

Turbellaria

• free living platyhelminthes

• ex: planaria

Neodermata

• parasitic platyhelminthes

• can be endo or ectoparasites

• in endoparasites, they are resistant to hosts digestive enzymes in order to survive

• endo parasites also have no eyespots

What are the two major Neodermata subgroups?

class trematoda and class cestoda

Trematoda (Flukes)

• 1mm to 8cm small

• endoparasites (feeds off of RBCs)

• takes food in through mouth

• most life cycles have multiple hosts

Step 1 Fluke Life Cycle

Numerous eggs are put in the environment through feces that contain miracidium and into the water

Step 2 Fluke Life Cycle

miracidium hatches after being eaten by a snail

Step 3 Fluke Life Cycle

sporocyst forms (inside snail)

Step 4 Fluke Life Cycle

redia forms (inside snail)

Step 5 Fluke Life Cycle

Cercaria burrows inside of muscles of fish after leaving the snail

Step 6 Fluke Life Cycle

metacercarial cysts in fish muscles form

Step 7 Fluke Life Cycle

raw, infected fish is consumed by humans or other mammals

What are the terms associated with the asexual reproduction of the oriental liver fluke?

miracidium, rediae, cercaria

What is the latin name for the oriental liver fluke?

clonorichis sinensis

miracidium

ciliated stage in egg

rediae

non-ciliated larvae produced within sporocyst

cercaria

tadpole-like larval stage

What happens in the second part of the complex life cycle of the liver fluke?

• larval maturation in fish (2nd intermediate host)

• then sexual maturation and reproduction in humans (primary hosts)

What is the 1st intermediate host for a liver fluke?

snails

metacercaria

juvenile stage produce within cysts

What are some common characteristics of liver flukes?

• lives in bile ducts of liver of humans, cats, dogs, and pigs

• common in Asia

• individual flukes can live 15-30 years in the liver

What are some facts about what happens when the liver fluke enters a human body?

• typically asymptomatic

• heavy infestation can lead to cirrhosis and death

• increases chances of liver cancer

What is cirrhosis?

scarring of the liver

What is the genus name for blood flukes?

schistosoma

How many species of what type of animal can cause the disease schistosomiasis?

3 species of blood flukes

What organism carries schistosomiasis?

freshwater snails

where do blood flukes usually live?

in blood vessels associated with the intestine or bladder

what are the symptoms of blood fluke infestation?

• itchy or skin rash after 1st contact (Burrow into RBCs)

• 1-2 months: fever, chills, muscle aches, cough

• chronic: damage to intestine and bladder

How do the worms keep themselves from being detected by the immune system?

worms coat themselves with the host’s own antigens which makes them immunologically invisible

What class do tapeworms belong to?

cestoda

What part of what organism is shown here?

The scolex of a tapeworm

What are the top two arrows pointing at?

hooks

What is the middle arrow pointing at?

the sucker

What is the top arrow pointing at and showing?

shows that the scolex is attached to the intestinal wall

What are the bottom three arrows pointing at?

Repeated proglottid sections

What is this a zoomed in picture of and on what animal?

One proglottid region on a tapeworm

What is the top arrow pointing at?

uterus

What is the middle arrow pointing at?

genital pore

What are some basic characteristics of tapeworms?

• most species live in the intestines of vertebrates

• no digestive cavity or enzymes

• long flat bodies divided into three zones

What are the names of the three zones in a tapeworm?

scolex, neck, and proglottids

Scolex

attachment organ, almost like suckers or clips to hold on to the intestine walls

no mouth

Neck

unsegmented portion of the tapeworm

Proglottids

repetitive sections of the tapeworm

Characteristics of proglottids

• each a complex hermaphroditic unit

• active growing zone in neck

• posterior proglottids form mature eggs

What is the name of the beef tapeworm?

taenia saginata

How does the beef tapeworm get passed to humans?

• juvenile in cattle muscle and burrow through instestines to muscles

• passed to humans when eating undercooked beef

• becomes adult in human intestines and pass between humans to cows through feces

How long are the tapeworms viable in feces?

up to 5 months

What is a pseudocoelomate?

they have a pseudocoel, which is a cavity between the mesoderm and endoderm

What does the pseudocoel serve as?

a hydrostatic skeleton against which the animal’s muscles can work

What do pseudocoelomates lack and what makes up for it?

they lack a defined circulatory system which is covered for by fluids which move within the pseudocoel

What phylum do roundworms belong to?

nematoda