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Biological Sciences 318 - Parasitology Lab Platyhelminthes 2

Biological Sciences 318 - Parasitology Lab Platyhelminthes 2. Kingdom: Animalia (unranked): Protostomia (unranked): Spiralia (unranked): Platyzoa Phylum:. Platyhelminthes. Characteristics: 1) simplest bilaterally symmetrical animals

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Biological Sciences 318 - Parasitology Lab Platyhelminthes 2

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  1. Biological Sciences 318 - Parasitology Lab Platyhelminthes 2

  2. Kingdom: Animalia • (unranked): Protostomia • (unranked): Spiralia • (unranked): Platyzoa • Phylum:

  3. Platyhelminthes Characteristics: 1) simplest bilaterally symmetrical animals 2) 3 layers fundamental cell layers (ectoderm, endoderm, mesoderm) 3) Body contains no internal cavity 4) Dorsoventrally flattened (diffusion) 5) Possess a blind gut (i.e. it has a mouth but no anus) 6) Protonephridial excretory organs (flame cell) 7) Elaborate nervous system (allows for invasion of a variety of habitats) 8) Reproduction mostly sexual as hermaphrodites 9) Inability to synthesize fatty acids (commensals or parasites)

  4. Class Monogenea • ectoparasites of aquatic poikilotherm vertebrates (skin & gill of fishes) • feed on mucus, epithelial cells, blood from wounds inflicted by their hooks • serious pathology and economic loss in artificial situations such as fish hatcheries •  blood loss, erosion of epithelium, secondary bacterial and fungal infections • 1-host direct life cycles (egg, oncomiracidium, adult; some viviparous) • anterior: reproductive and digestive organs; posterior: opisthohaptor (holdfast)

  5. Class Trematoda • oral suckers for attachment to their vertebrate hosts /sometimes with hooks • all trematodes are parasitic, and most adult trematodes parasitize vertebrates • dorso-ventrally flattened (adults) • sexual and asexual reproductive phases (adults) • entire interior is occupied by the reproductive system

  6. Trematoda • largest and most medically and economically important group • blood flukes (Schistosomes  most serious helminth human parasite), liver flukes (Fasciola), intestinal flukes (Echinostomes), lung flukes (Paragonimus) • complex life cycles involving number of juvenile stages that are parasitic in one, two, or more intermediate hosts before reaching adulthood, at which time they parasitize a definitive host (vertebrate; bile ducts, alimentary & respiratory tract, blood vessels) • diet consists of blood, mucus and surface epithelial cells

  7. Digenea • Organs of attachment: • oral sucker and acetabulum (ventral) • Digestive system: • mouth, pharynx, esophagus • intestinal ceca • Excretory system: • Protonephredia, excretory pore • Reproductive system: • ♂ • Testes • Vasa efferentia • Vas deferens • Cirrus pouch containing • Seminal vesicle, Cirrus • ♀ • Ovary • Oviduct • Mehlis gland • Ootype • Uterus • Vitellaria • Vitelline ducts • Seminal receptacle • Laurer’s canal

  8. Digenea • Basic digenean life cycle: Eggmiracidiumsporocyst or redia---daughter sporocysts-cercariaemetacercariaeadults • 1-4 intermediate hosts (1st mollusc; asexual reproduction) • The molluscan host is almost always castrated: • --physically (rediae) • --chemically (sporocysts) • sexual reproduction in vertebrate definitive host

  9. Learning Objectives • 1 .Know general characteristics • Compare monogenea and digenea • 2. Monogenea • One host simple life cycle • Host, life cycle stages, anatomy • Dactylogyrus: host, host tissue, economic importance, visual id • 3. Digenea • 2+ hosts, complicated life cycle, 1st intermediate: mollusc • General morphology and function: reproductive organs vary and can be used for identification • Larval stages: anatomy, form and function, hosts, visual id • 4. Family Dicrocoeliidae (liver flukes) • Dicrocoeliumdendriticum • General characteristics • Tissue in definitive host • Life cycle • How does this species alter its intermediate host behavior to increase chance of transmission • Visual id • 5. Family Opisthorchiidae (liver flukes) • Chlonorchissinensis • General characteristics • Life cycle • Tissue infected • Visual id • 6. Family Echinostomatidae (intestinal flukes) • Know that they are spinous • Echinostomarevolutumslide • Hosts: low host specificity • Tissues infected • Visual id • 7. Family Fasciolidae • General characteristics as they apply to the two species • Visual id, life cycles, compare and contrast F. hepatica and F. buski • 8. Family Schistosomatidae (blood flukes) • Dioecious with sexual dimorphism • General characteristics • Schistosomamansoni: tissue in definitive host • Visual id: male, female, in copula - find eggs in intestine and liver • Know that these eggs cause the pathology • Life cycle • Other examples of Schistosomes, diagnostic feature (eggs) and pathologies • 9. Family Troglotrematidae (lung flukes) • Tissue infected in definitive host, visual id , life cycle, host, Paragonimuswestermani Vocabulary Monoecious Dioecious Oncomiracidium Opisthaptor Prohaptor Acetabulum Operculum Miracidia Sporocyst Rediae Cercariae Metacercariae

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