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BIOL 3454: Chapter 14
diploblastic
|
two tissue layer
|
triploblastic |
three tissue layer
|
protostomia
|
blastopore forms mouth
|
deuterstomia |
blastospore forms anus
|
Phylum Acoelomorpha
|
P: Acoelomorpha
-small flat worms (not flatworms)
-live in marine sediments; few pelagic |
Acoelomorpha Characteristics part 1
|
•Rootlets of epidermal cilia form interconnecting network
•Most free living, some commensal, some parasitic
•Bilateral symmetry, body flattened dorsoventrally, anterior concentration of nerve cells
•Epidermis cellular
•Gut absent or incomplete and saclike |
Acoelomorpha Characteristics part 2
|
•Mesdermal muscle cells: longitudinal, circular, diagonal
•Radially arranged nerve cords
•Asexual reproduction by fragmentation
•Monoecious sexual reproduction via internal fertilization
•No excretory or respiratory system |
Phylum Playhelminthes
|
P: Playhelminthes
from platys=flat & helmins=worms
-real flat worms
-free living or parasitic |
Turbellaria |
-cellular, cilliated epidermis
-rhadbites - rod shaped, fill with water for protection
-dual gland adhesive organs
glands for adhesion
glands for unsticking
-have multiple types of muscle fibers under epidermis
-digestion is extracellular and intracellular |
Parasitic flatworms
|
-syncytial teguments as a covering
many nuclei in a single cell membrane
resistant to the immune system of the host
-have multiple types of muscle fibers under epidermis
-no digestive system
rely on host to break down food
many have blind ended intestine
-digestion is extracellular and intracellular |
protonephridia |
flatworms use ... for simple waste excretion and osmoregulation
-most waste excreted across body wall |
flame ell
|
Protonephridia has a unique flame cell that is shaped like a cup with a tuft of flagella
-Flagella draws fluid through the weir, which acts as a collecting net for particles |
Nervous and sensory systems
|
some have longitudinal nerve cords
-nerves organized into distinct types
sensory
motor
association
well developed tactile and chemo reception
more developed senses than cnidarians |
Ocelli |
photosensitive eyespots
|
statocyts |
equilibrium |
rheoreceptors |
sensing water currents
|
Phylum Platyhelminthes
|
-flatworms, free-living turbellarians, parasitic flukes, tapeworms
-most marine but some freshwater
-acolemates
-digestive gut to present with no anus
-bilateral symmetry
-first to have cephaliztion (sensory/nervous tissue into head end of body)
-three tissue layers: endoderm, mesoderm, ectoderm |
Phylum Platyhelminthes Reproduction
|
Reproduce Sexually & Asexually
-asexual (great regenerators)
fission
fragmentation
-sexual
most monecious but cross fertilize
most have free swiming larve |
Class Turbellaria
|
P: Platyhelminthes
C: Turbellaria
-mostly free living worms
-creep along that use muscles and cillia to move |
Class Trematoda (Subclass Digenea)
|
P: Platyhelminthes
C: Trematoda
SC: Digenea
-All parasitic flukes; almost all are adult vertebrate parasites.
-Many species of medical and economic importance
-complex life cycle
-intermediate and definitive hosts
Adults inhabitat lots of organ systems
digestive,respiratory, circulatory, urinary, and reproductive. |
Genus clonorchis
Subclass digenea |
P: Platyhelminthes
C: Trematoda
SC: Digenea
genus clonochis
-human liver fluke
-ingested via undercooked fish
-Intermediate host: snail
-final host: vertebrate |
Clonochis -human liver fluke
|
Shelled embryo or larvae excreted to water
Miracidium (free swimming larvae) turn into sporocyst.
Sporocyst penetrates snails (mollusks) and reproduce asexually creating more sporocyst or rediae.
Rediae reproduce asexually making cercariae
develop into metacercariae (juvenile flukes)
Juveniles eaten by host and mature, repeat cycle.
Later cercariae encyst in fish and is eaten by human host. Encyst into duodenum
|
genus Schistoma Subclass Digenea
|
P: Platyhelminthes
C: Trematoda
SC: Digenea
genus schistoma
human blood fluke
-dioecious (seperate houses)
-intermediate host: snail
-definitive host: humans/vertebrates
-cercaira penetrates skin, infect the intestinal veins and cause enlargement of other organs- |
Schistoma - blood fluke
|
Eggs discharged in human waste
if they make it into water, hatch as miracidia
Miracidia get into snail
creating sporocyst which makes more sporocyst
give rise to cercariae; NO REDIAE
cercariae swim until contact human skin
burrow in, find blood vessel, and burrow into that vessel
Swims to the hepatic portal system where they can live in the liver
adults move to the interface of digestive and circulatory system and discharge eggs. |
Swimmer's itch
|
-North American natural lakes
-Normal hosts are birds
-bore into humans by mistake
die, releasing irritating chemicals
resembles mosquito bites |
Paragonimus - lung fluke
|
Eggs coughed out of lungs, swallowed, eliminated through feces
Zygotes develop in water
Miracidium finds snail
Miracidium, then rediae, then cercariae
Cercariae shed into water or ingested by crabs eating snails
Metacercariae develop in crabs
You eat undercooked crab, get them, and they migrate to lungs, can be fatal |
Class Monogenea
|
P: Platyhelminthes
C: Monogenea
-All parasites, usually on gills of fish. Few in turtles, frogs, and hippos eyes.
-Usually not terrible for host
-Direct life cycle
egg makes ciliated larvae called oncomiracidium
hooks to host on posterior end with an opisthaptor |
opisthaptor
|
P: Platyhelminthes
C: Monogenea
-hooks to host on posterior end that is located on the oncomiracidium (ciliated larvae) |
oncomiracidium |
P: Platyhelminthes
C: Monogenea
-the ciliated larva the egg hatches into.
-it attaches to a host sometimes following a free swimming stage (flatworm- monogenea) |
Class Cestoda
|
P: Platyhelminthes
C: Cestoda
-tapeworms
front end is a scolex with hooks for attatchment
repeating reproductive segments called proglottids, chain of these is the strobila
-no digestive system
-entire body covered in microtriches
-self fertilize, but prefer cross fertilization
-eggs or entire proglottid shed in feces of host |
Scolex |
P: Platyhelminthes
C: Cestoda
-hooks for attachedment |
proglottids |
P: Platyhelminthes
C: Cestoda
-repeating reproductive segments
chains of this is strobilia |
Phylogeny of Playhelminthes
|
Turbellaria is paraphyletic
|
Planuoid ancestor hypothesis
|
–One branch becomes radially/biradially symmetrical and becomes Cnidaria, other branch becomes bilaterally symmetrical and becomes Platyhelmonthes.
|
Platyhelminthes |
-Platyhelminthes may not be monophyletic
Parasitic
trematoda
monogenea
cestoda |
Phylum mesozoa
|
fr mesos=middle & zoon=animal
-missing link between protozoa and metazoa
-all parasites or symbionts
20-30 cells in two pairs
-two groups
rhombozoans
orthonectids |
rhombozoans |
Cephalopod mollusc kidney parasites, life cycle:
vermiform adults asexually make larvae that grow and sexually reproduce under crowded conditions. Larvae shed in host urine into water. |
Orthonectids |
Invertebrate parasites, life cycle:
sexual and asexual phases, asexual phase known as a plasmodium, divides to form distinct males and females |
Phylum Nemertea
|
P: Nemertea
-ribbon worms
-fr greek nemertes = one of the nereids, unerring one
-refers to sharp aim of proboscis
-thread or ribbon shaped
-bilaterally symmetrical worms
-several meters in length
-live in gelatinous tubes made of self secreted material |
Nemertean Characteristics pt 1
|
•Eversible proboscis, unique to Nemerteans
•Mostly free living, a few parasitic
•Bilateral symmetry, cylindrical anteriorly and flattened posteriorly
•True coelomic cavity called a rhyncocoel
•Complete digestive system
•Four lobed brain
|
Nemertean Characteristics pt 2
|
•Sensory ciliated head slits
•Asexual reproduction by fragmentation
•Sexes separate, pilidium larvae
•Flame cells
•Blood vascular system
•No respiratory system |
Nemertean basics
|
-glide over slime trails
-mouth anterior and ventral; digestive tract complete
-cilia move food through intestine. digestion mostly extracellular in gut lumen
-seize prey with a proboscis, and pulled into rhynchocoel
-True circulatory system; blood flow maintained by body movements and contractions of body walls. |