Flatworms and Roundworms. ANCESTRAL PROTIST Porifera Ctenophora Cnidaria Acoela True Tissues Metazoa...
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Transcript of Flatworms and Roundworms. ANCESTRAL PROTIST Porifera Ctenophora Cnidaria Acoela True Tissues Metazoa...
Flatworms and Roundworms
ANCESTRALPROTIST
Porifera
Ctenophora
Cnidaria
Acoela
True Tissues
Metazo
a
Eu
metazo
a
Bilateria
Hemichordata
Echinodermata
Chordata
Platyhelminthes
Rotifera
Ectoprocta
Brachiopoda
Mollusca
Annelida
Nematoda
Arthropoda
Deu
tero
stom
ia
Lo
ph
otro
cho
zoa
Ecd
ysozo
a
Single common animal ancestor
prot
osto
mes
inve
rteb
rate
s
•Bilateral at some point•Usually cephalized •Triploblastic development
Terms of location (for bilateral organsims)
FLATWORMS (phylum platyhelminthes)
• Flattened body plan– Puts all cells close to ext. env. or GVC– No need for respiratory or circulatory systems– Gas exchange across ext. surface and gastrodermis
• Free living• Parasitic forms• Aceolomates (no body cavity)• Most belong to Rhabditophora
Digestive System• Gastrovascular Cavity—incomplete digestive
system• Highly branched (diverticula)• Functions– Digestive chamber • most digestion occurs extracellularly
– distributes nutrients
Excretory System & Water Balance• Protonephridia • flame bulbs internal external env. through pores• In freshwater species for maintaining water balance• Some parasitic flatworms are isotonic with host and
protonephridia eliminate nitrogenous waste
• Interstitial fluid cap cell of flame bulb eliminated via ducts and pores
• Nervous System:– Dual ventral nerve cords– “brain of ganglia”
• Reproduction;– Mostly cross fertilizing hermaphrodites– Some parasitic forms are dioecious
CNS
Planariafree living Rabditophora
• FREE LIVING RABDITOPHORA• predators and scavengers• move w/ ventral cilia & mucus• Sense Organs & NS
– Photoreceptors (eyes)– Lateral flaps (auricles) that are chemoreceptor's
Trematodes• Intermediate and final (ultimate) host– Blood flukes (schistosoma), liver flukes
• epicuticle of proteins and lipids instead of epidermis– digestion by the digestive enzyme in hosts
Schistosoma: unique among trematodes; are dioecious with distinct sexual dimorphismLarge male that surrounds femaleFemale is enclosed within the males gynacophoric canal for entire life of worms where they reproduce sexually.
Figure 33.11Humanhost
Male
Female
1 mm
Mature flukes
Ciliatedlarva
Motilelarva
Snail host
Tapeworms• Mostly inside vertebrates• Scollex for attachment• No GVC; direct absorption of nutrients• Proglottids = reproductive segments• Reproduction is usually sexual between proglottids of
adjacent individuals
Tapeworms
Roundworms (phylum Nematoda)Bilateria-protostoma-ecdysozoa
• Cyclinderical shaped bodies that taper to tips at both ends• Psuedocoel• Usually dioecious• Free living in soil, fresh, and salt water
– decomposers: important ecological role as decomposers• Many important parasitic forms
– Parasitize crop plants– Parasitize humans (~50 species)
• e.g., trhinella spiralis—trichinoisis
– Parasitize non-human animals– Parasitic forms manipulate host cells
BODY COVERING• Cuticle (collagen based) that must be shed– Ecdysis/molting
GAS AND WASTE EXCAHNGE• Directly across body wall (gas & nitrogenous
wastes)• Some species w/ glands to excrete salt
No circulatory system• Nutrients transported by fluid in psuedocoel.
Digestive System
• Complete digestive tract (alimentary canal)• Continuous feeding• Specialized regions/organs– Mouth, sucking pharynx, intestines, rectum, anus– Contents propelled by body movements
Nervous system• 4 nerve cords + “brain” of neuron cluster
surrounding pharynx. • ventral nerve largest
Muscles:• Longitudinal muscles only • Psuedocoel acts as a hydrostatic skeleton
Schistosomiasis, also known as bilharzia, snail fever, and Katayama fever
Schistosomiasis affects almost 210 million people worldwide,[5] and an estimated 12,000[6] to 200,000 people die from it a year.[7] The disease is most commonly found in Africa, as well as Asia and South America.[3] Around 700 million people, in more than 70 countries, live in areas where the disease is common.[7][8] Schistosomiasis is second only tomalaria, as a parasitic disease with the greatest economic impact.[9] It is classified as a neglected tropical disease.[10]