Lab 3 - Flatworms and Roundworms

worm

any invertebrate with a long, cylindrical, soft body

protostome

mouth first

mouth forms from blastopore

deuterostome

mouth second

anus forms from blastopore

body cavity

fluid-filled or air-filled space between the digestive tract and the external surface

body cavity functions

structure, transport of nutrients and gases, movement, cushion organs

acoelomate

don’t have a cavity outside the digestive tract

pseudocoelomate

have a body cavity

only surrounds one side

bilateral symmetry

one plane of symmetry

anterior, posterior, dorsal, ventral

associated w/ cephalization & central nervous system

cephalization

development of a head

at the anterior end

central nervous system (CNS)

concentration of sensory organs and neural processing in head

coordinates movement

bilaterian lifestyle

typically move around in their environment

flatworms & roundworms have either

ganglia & nerve cords or nerve ring & nerve cords

organ systems

have nervous, muscular, digestive, reproductive systems

no circulatory system

endoparasites

live within their host

ectoparasites

live on the external surface of their host

parasites face unique challenges

getting into host

reproduction

effects on host

definitive host

houses adult parasite

intermediate host

houses larval (immature) stages

• multiple larval stages

• can be multiple intermediate hosts

flatworm characteristics

acoelomate

gastrovascular cavity

gas exchange

nervous system

movement

reproduction

free-living or parasitic

flatworm gastrovascular cavity

delivers nutrients and O₂ throughout body

mouth (no anus) - incomplete digestive system

flatworm gas exchange

through epidermis

need aquatic/damp environments

dorso-ventrally flattened

flatworm nervous system

ganglia & 2 ventral nerve cords

flatworm movement

set of muscles: circular, longitudinal, dorso-ventral

cilia & mucus for movement

flatworm reproduction

some are hermaphroditic

some have separate sexes

hermaphroditic

one individual has both male and female reproductive organs

planarians

free-living

eyespots

sensory lobe

pharynx

eyespots (ocelli)

sense light and dark

sensory lobe (auricle)

sense chemicals

pharynx

muscular tube used to ingest prey

opens at the mouth

mesenchyme

tissue that develops from the mesoderm

flukes

parasitic

specialized epidermis

suckers

much of the body is reproductive organs

intermediate/definitive hosts

specialized epidermis

resistant to host immune system

suckers

for attachment to hosts

flukes life cycle

intermediate hosts - typically snails

definitive hosts - vertebrates

sheep liver fluke

hermaphroditic

genital pore

seminal receptacle

genital pore

opening for reproductive systems

seminal receptacle

stores received sperm

blood fluke

causes schistosomiasis in humans

causes severe anemia

tapeworm

hermaphroditic

extensive reproductive system

digestive and nervous system are degenerate

no respiratory & circulatory systems

scolex

anterior end with suckers and hooks

proglottids

segments

each segment is hermaphroditic

roundworm characteristics

pseudocoelomate

complete digestive system (mouth & anus)

gas exchange (same as flatworm)

nervous system

movement

reproduction

excretory system

cuticle

roundworm nervous system

nerve ring & dorsal and ventral nerve cords

roundworm movement

set of muscles: longitudinal

roundworm reproduction

most species have separate sexes

roundworm excretory system

tubes and pores for eliminating waste

cuticle

a tough outside layer

ascaris

all stages develop within the same host

common in pigs and humans

separate sexes - focus is on females

female ascaris

2 ovaries

2 oviducts

2 uteri

• uteri come together at the vagina

trichinella

whole life cycle can occur in one host