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Acoelomate vs. pseudocoelomate vs. eucoelomate
- Coelum: space between gut and epidermis completely surrounded by mesoderm
- Acoelomate: “without coelum” – space between gut and epidermis is FILLED with mesoderm
- Pseudocoelomate: “false coelum” – space between gut and epidermis has mesoderm only on outside (other side is endoderm).
- Eucoelomate: “true coelum” – space between gut and epidermis is completely surrounded by mesoderm.
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Characteristics of acoelomate animals + phyla
- Some cephalization (have head)
- Bilateral symmetry
- Have true organs
- Protostome (“mouth first”)
- Spiral cleavage
- Simplest excretory and circulatory system
- Triploblastic – Mesoderm in the form of parenchyma (muscle fiber and mesenchyme)
- Three phyla – Platyhelminthes, Nemertea, Gnathostomulida
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Platyhelminthes – germ layers? Symmetry? Digestion? Symbiosis? Reproduction? Lifecycle? Special cells/structures? Other?
- Triploblastic (Mesoderm in form of parenchyma layer)
- Bilateral symmetry (Flat dorsoventrally)
- Incomplete digestive system in some (mouth, no anus) – waste can exit through mouth OR diffuse through body walls OR flame cells -> excretory canal -> excretory duct (Protonephridia)
- Free-living and parasitic
- Most monogenea are ectoparasitic of fish (cause infestation)
- All digenea and cestoda are endoparastic (cause infection)
- Most are monecious (hermaphroditic) – not Schistosoma
- Indirect (needs vector) and direct lifecycles
- Definitive host is vertebrates in most cases (sexual reproduction occurs)
- Some have eyespots (light intensity, not image-forming)
- True muscles
- Body fluid moves by muscular contraction (similar to skeletal-muscle pump for veins)
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What are the classes within phylum Platyhelminthes? List specific genera associated with each class
- Turbellaria: Dugesia
- Trematoda:
- Subclass Digenea: Fasciola hepatica, Fasciolopsis buski, Clonorchis sinensis, Schistosoma mansoni, Shistosoma japanicum, Shistosoma haematobium, Paragonimus westermani
- Subclass Monogenea: Gyrodactylus cylindriformis
- Cestoda: Taenia saginata, Taenia solium, Diphyllobothrium latum, Echinococcus granulosus, Dipylidium caninum
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Class Turbellaria – Example? Symbiosis? Habitat? Cilia? Digestive system? Osmoregulation? Nervous system? Reproduction? Feeding style? Special cells/structures?
- Planarians (eg. Dugesia)
- Free-living
- Mostly marine
- Epidermis is ciliated on ventral side
- Mouth on ventral side, no anus (incomplete digestive system)
- Metabloic waste by diffusion through the body wall OR flame cells OR mouth
- Osmoregulation required for Planaria because water is constantly entering (like Paramecium)
- Flame cells (part of excretory system) remove water and waste (ammonia) for osmoregulation
- Three types of neurons: sensory, motor, and association
- Have neural ganglia, NOT brain
- Asexual regeneration (cut in half = 2 organisms)
- Monoecious, but practice cross fertilization to increase genetic variability
- Fertilization is internal, and occurs in female oviduct
- Simple life cycle
- Carnivorous heterotrophs
- Ocellia (light-sensitive eyespot)
- Rhabdites cells (release mucus to ease locomotion)
- Three types of muscle: longitudinal, circular, and radial
- Gastrodermis has phagocytes to engulf food
- Protonephredia = flame bulbs
- Pharynx (in middle of animal) can extend and act as a vacuum for food.
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Class Trematoda – common name? Symbiosis? Cilia? Special cells/structures? Other?
- Common name “flukes”
- All parasitic
- Tegument (“skin”) has no cilia and is syncytial (mutli-nucleated)
- Have two suckers (oral and ventral)
- Poorly developed sense organs
- Subclasses Digenea and monogenea
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Subclass Digenea – Life Cycle? Species? General lifecycle? Why?
- Require two hosts (intermediate host and definitive host)
- Species include Fasciola hepatica, Fasciolopsis buski, Clonorchis sinensis, Schistosoma sp., Paragonimus westermani
- General lifecycle: egg (contains miracidium) -> miracidium (ciliated larval stage that escapes egg, gets into water, and finds/penetrates snail) -> sporocyst (in snail, contains many rediae) -> rediae (in snail, contains many cercariae) -> cercariae (ciliated larva that gets out of snail) -> metacercaria encyst on vegetation or meat of fish -> adult in human
- This type of lifecycle allows a single egg to rise to MANY progeny. Since odds of infection are not high, this increases odds of survival. Flukes are only animal where single egg can become multiple organisms.
- Stopping the spread of flukes requires removing one of their intermediate hosts from the environment.
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Fasciola hepatica – Common name? Taxonomy? Host? Detection? Specific lifecycle?
- Disease common name is “liver rot”
- Phlylum Platyhelminthes, class Trematoda, subclass Digenea
- Animals (sheep, cow, etc) Not typically found in human
- Causes large white spots on liver of animal. Animal probably got infected by eating grass that had metacercaria.
- Lifecycle: Cow poops egg -> egg in water -> miracidium escapes egg, find snail (Lymnea) -> penetrates snail -> becomes sporocyst within snail -> many rediae develop from single sporocyst -> inside rediae are many cercariae -> cercariae exits, finds vegation -> becomes metacercaria -> eaten by cow -> matures to adulthood in liver of cow -> cow poops egg…
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Fasciolopsis buski – Taxonomy? Host? Compare to Fasciola hepatica? Lifecycle?
- Phlylum Platyhelminthes, class Trematoda, subclass Digenea
- Found in human small intestine
- Larger than Fasciola hepatica
- Lifecycle: Human poops egg -> egg in water -> miracidium escapes egg, find snail -> penetrates snail -> becomes sporocyst within snail -> many rediae develop from single sporocyst -> inside rediae are many cercariae -> cercariae exits, finds vegation -> becomes metacercaria -> eaten by human -> matures to adulthood in small intestine -> human poops egg…
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Clonorchis sinensis – Common name? Taxonomy? Lifecycle? Symptoms? Location?
- Common name “Human liver fluke”
- Phlylum Platyhelminthes, class Trematoda, subclass Digenea
- Lifecycle: human poops egg -> egg in water -> miracidium escapes egg, find snail -> penetrates snail -> becomes sporocyst within snail -> many rediae develop from single sporocyst -> inside rediae are many cercariae -> cercariae exits, finds fish -> penetrates fish, becomes metacercaria -> eaten by human -> matures to adulthood in bile duct of human -> human poops egg…
- Note – Metacercaria found in meat of fish, not vegetation
- Human can only become infected through ingestion of infected fish (Cooking will kill – pickling will not)
- Doesn’t harm fish
- Adult in bile duct, doesn’t cause an issue if only a few, but many will block the bile duct
- Issue in rural areas of far eastern countries
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Give two reasons why tegument is beneficial to Platyhelminthes.
- Constantly change surface protein molecules, making host antibodies useless
- Can absorb food THROUGH tegument
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Schistosoma – taxonomy? Common name? Reproduction? Species/location/geo. Location? Symptoms? Life cycle?
- Phlylum Platyhelminthes, class Trematoda, subclass Digenea (Old name Bilharzia)
- Common name “blood flukes”
- Dioecious w/ male bigger (wider) than female
- Male has gynecophoric canal – females enter and reside during reproduction
- S. mansoni: found in blood vessels of large intestine. Can kill humans. Causes bloody feces. [far eastern countries]
- S. japanicum: in blood vessels of small intestine. Can kill humans. Causes bloody feces. Can cause dwarfing. [far eastern countries]
- S. haematobium: in blood vessels of urinary bladder. Causes bloody urine (maturity in old Egypt). [Middle east/North African countries]
- Cause ulceration in intestine, bladder
- Schistosoma Dermatitis: (disease, not species) Schistosoma of a bird exits in feces, gets into water, cercaria enter human causing an itch, but die within 24 hours. [North America]
- Do not have metacercaria and rediae stages
- Lifecycle: human poops egg -> egg in water -> miracidium escapes egg, find snail -> penetrates snail -> becomes sporocyst within snail -> inside sporocyst are many cercariae -> cercariae exits, finds human -> matures to adulthood in human -> Schistosoma sexually reproduce -> human poops egg…
- Cercaria have branched tails
- Method of biological control would be crayfish, to remove the snails (intermediate hosts)
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What are the 6 major diseases according to WHO?
- Schistosomiasis, malaria, filariasis, trypanosomiasis, leishmaniasis, and leprosy
- 5 are parasites, only 1 (leprosy) is bacteria
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Paragonimus westermani – Taxonomy? Common name? Life cycle?
- Phlylum Platyhelminthes, class Trematoda, subclass Digenea
- Common name “lung flukes”
- Adult fluke resides in lungs (human)
- Crab/crayfish is intermediate host – metacercaria reside in meat. Human is definitive host (infection from eating crab or crayfish without cooking)
- Metacercaria stage goes to human lung and matures into adults
- Two methods of egg release…
- 1. Escape through sputum (cough up/sneeze)
- 2. Sputum is swallowed, egg goes to digestive system, excreted in feces.
- Either way, egg gets into water and lifecycle is continued
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Subclass Monogenea - Species? Lifecycle?
- Species include Gyrodactylus cylindriformis
- All parasitic on gills or external surface of fish, suck blood of fish
- Ectoparasitism and infestation (outside) NOT infection (inside)
- Direct life cycle, single host (just fish)
- Egg -> single larva (oncomiracidium) -> matures on gills of fish -> adult -> detaches and makes eggs
- Opisthaptor: structure that attaches to fish gills and sucks blood
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Class Cestoda – Species? Common name? Gross anatomy? Reproduction? Lifecycle? Digestive system? Other?
- Species include Taenia saginatus, Taenia solium, Diphyllobothrium latum, Echinoccous granulosus, Dipylidium caninum
- Commonly named “tapeworms”
- Three major parts: scolex (“head area” that has can have suckers and/or hooks for attachment), germinative zone (“neck area” where asexual reproduction occurs, lengthening tapeworm), strobila (“tail area” consisting of chains of proglottids)
- Scolex may contain rostellum (elevation of scolex)
- Immature proglottids -> mature proglottids (have testes, ovary, yolk gland, etc) -> gravid/ripe proglottids (uterus filled with eggs fills proglottid and all other structures disintegrate)
- Gravid proglottids are ‘released’ by the cestode and exit in the feces, releasing eggs.
- Nearly all are monoecious (hermaphroditic)
- Cross fertilization is possible
- Adults are found in vertebrates, intermediate hosts are invertebrates
- Nearly all organisms can have a tapeworm (different species)
- No digestive system, food absorbed through tegument
- In general, do not harm host simply compete for food.
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Taenia saginata – Phylum? Class? Common name? Host(s)? Disease? Anatomy? Life cycle? Other info?
- Phylum Platyhelminthes, class Cestoda
- Common name “beef tapeworm”
- Intermediate host – cattle, definitive host – human
- Does not harm human
- Scolex has 4 suckers, no hooks
- Cysticercus (larval stage, infective for human) in beef
- Excretory ducts have flame cells
- Life cycle: egg -> bladder worm/cysticercus (in cattle) -> cysticerci becomes adult and sheds gravid proglottids (in human)
- Human ingest cysticerci from uncooked infected beef, cattle ingest egg from human feces
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Taenia solium – Phylum? Class? Common name? Host(s)? Disease? Anatomy? Life cycle? Other info?
- Phylum Platyhelminthes, class Cestoda
- Common name “pork tape worm”
- Intermediate host – pig OR human, definitive host – human
- Cerebral cysticercosis: cysticercus in human can go to brain rather than other parts of the body causing devastating effects. Cannot be removed by surgery.
- Scolex has rostellum, suckers, and hooks
- Life cycle: egg -> oncospheres -> bladder worm or cysticercus (in pig) -> cysticerci becomes adult and sheds gravid proglottids (in human)
- Note – cysticercus is also possible in human IF human ingests egg. (egg -> cysticercus)
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Diphyllobothrium latum – Taxonomy? Host(s)? Symptoms? Anatomy? Life cycle?
- Phylum Platyhelminthes, class Cestoda
- Intermediate host – fish, definitive host – human
- Competes with vitamin B12, which is needed for proper RBC production.
- Causes megaloblastic/pernicious anemia (RBCs become huge, unable to fit into capillaries)
- Lack of gas exchange results in lethargy, tiredness, etc but not death.
- Scolex has longitudinal grooves (no suckers/hooks)
- Cysticercus in fish
- Infection by eating infected raw fish (especially in the Great Lakes area)
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Echinococcus granulosus – Taxonomy? Host(s)? Symptoms? Anatomy? Other?
- Phylum Platyhelminthes, class Cestoda
- Definitive host – dogs and other canine, intermediate host – human
- Hydatid cyst: cysticercus in human becomes HUGE. Can only be removed by surgery (no medication). If hydatid cyst ruptures during surgery, patient will die instantly from anaphylactic shock.
- Smallest tapeworm in class, only 3 segments. Entire animal less than 1 cm.
- Possible infection by petting dog who has rolled in its infected feces -> eggs on hand -> hand in mouth
- Hydatid cyst can be formed in stomach, brain, arms, etc. Doesn’t HAVE to be one area.
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Dipylidium caninum – Taxonomy? Common name? Symptoms? Host(s)? Anatomy? Prevention?
- Phylum Platyhelminthes, class Cestoda
- Common name “dog tapeworm”
- Children can contract, but adult immune system will easily destroy. Would contract by eating infective flea.
- Intermediate host – flea, definitive host – dogs (mostly), some cats
- Gravid proglottids look like rice granules
- Good method of prevention is to place mothballs into a vacuum bag when vacuuming. This will kill the fleas, and end the cycle.
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Describe the adaptations cestodes have developed to be successful
- Do not harm hosts (in general)
- No GI tract, absorb nutrients through tegument
- Have cuticle to prevent digestion
- Have hooks/suckers for attachment to host
- Asexual reproduction results in thousands of eggs released in an “assembly line” type fashion via proglottids
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Compare/contrast Taenia solium and Taenia saginata
- T. solium: Intermediate host pig/human, definitive host human, cerebral cysticercosis, uterus branches less than seven times, scolex has 4 suckers/hooks/rostellum
- T. saginata: Intermediate host cow, definitive host human, does not harm human, uterus branches more than seven times, scolex has 4 suckers/no hooks
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