Transcript Lab4_Platyhelmintes_pre lab_presentation

Biological Sciences 318- Parasitology Lab
Platyhelminthes - Cestodes
Kingdom: Animalia
(unranked): Protostomia
(unranked): Spiralia
(unranked): Platyzoa
Phylum:
Turbellaria
(flat worms)
Platyhelminthes
Trematoda
(Digeneans)
Monogenea
(parasitic
flukes)
Cestoda
(tapeworms)
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) some 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 and sterols (commensals or parasites)
Cestoda
Tapeworms
• all endoparasitic (nearly every species of vertebrate)
• no mouth, no digestive system (only vestigal sucker and pharynx remaining)
• large reproductive system!
• absorb nutrients through tegument
Cestoda
Cestodaria
(monozoicunsegmented)
Eucestoda
(polyzoicsegmented)
Eucestoda
True tapeworms
Form and Function: a. Scolex with holdfast organelles (suckers, grooves, hooks, spines)
- 3 types of sucking depressions:
i- Bothria: shallow sucking grooves (Pseudophyllidea)
ii- Bothridia: 4 leaflike flexible structures (Tetraphyllidea)
iii- True suckers/acetabula (Cyclophyllidea)
b. Neck
c. Strobila (divided into proglottids)
Strobilation: Addition of new proglottids in neck region
Mature from AP
Apolysis: gravid proglottid breaks off releasing eggs
Alternatively eggs released through uterine pore.
Eucestoda
True tapeworms
Form and Function: Reproductive Systems
Order: Cyclophyllidae (Taenia spp.); Pseudophyllidae (Diphyllobothrium latum)
Eucestoda
True tapeworms
Form and Function: Development
• Two-phase life cycles:  intermediate
 definitive
1. Embryogenesis within egg results in larva  Oncosphere
2. Hatching of Oncosphere in intermediate host (extraintestinal site)
3. Metamorphosis into juvenile with scolex  Metacestode (1 to various
different stages)
4. Development of adult tapeworm in definitive host (intestinal site)
Eucestoda
True tapeworms
Order: Pseudophyllidae
• bothriate scolex (possessing dorsal and ventral groove = bothrium)
• Testes and vitellaria scattered throughout the proglottid
• The ovary is bilobed and posterior. Genital pores ventral
• An uterine pore present on dorsal or ventral surface
• Eggs are operculate and contain ciliated embryo, the coracidium
• Adult parasites of all classes of vertebrates, but fish are their primary host.
• The life cycle involves procercoid (larval stage often found in copepods) and plerocercoid
larval stage (found in fish)
 Diphyllobothrium latum (broad fish tapeworm)
Can be a serious pathogen, causing a pernicious anemia in human due to the worm absorbing
large amounts of vitamin B12
Eucestoda
True tapeworms
Order: Cyclophyllidea
• scolex that usually contains four suckers; rostellum is present or absent (may be armed)
• The genital pore is usually lateral; Vitelline gland is single, compact, and posterior to the ovary.
• Eggs develop into some form of bladderworm in invertebrate or vertebrate intermediate host.
• Common tapeworms of birds and mammals, although some are found in reptiles.
• Infective eggs contain an oncosphere larva that bears 6 hooks.
• Variety of intermediate host types, both invertebrate and vertebrate
P
A
Eucestoda
True tapeworms
Order: Cyclophyllidea
• Depending on cestode species: larval stage in the vertebrate intermediate host the
Metacestode: cysticercus, strobilocercus, coenurus (multiceps), hydatid or cysticercoid.
• Family Taeniidae, Genus Echinococcus, Family Dilepididae, Hymenolepididae, Anoplocephalidae
Taenia pisiformis
Hymenolepis diminuta
cysterceroid life stage
Hymenolepis diminuta egg
Diphyllobothrium latum
Taenia egg
Echinococcus granulosus
Diphyllobothriumltaum eggs
Echinococcus granulosus hyatid cysts
multilocular cyst
Dipylidium caninum
Review Session
Fri. Feb 6 1:00 – 4:00
Mon. Feb. 16 2:00-5:00
Lab Exam
Feb 17-19
(date varies by lab section)
Learning Objectives
1. Platyhelmintes - Flatworms
- Why are they flat? Why are they special?
- Know that reproductive structures are used in id!
2. Subclass Eucestoda
- Polyzoic; body parts; Strobilation
- Hermaphrodites or monoecious; compare eggs
- Difference between Cyclo- & Pseudophyllidae
3. Order Cyclophyllidae
- General characteristics
4. Family Taeniidae
- General charcterristics
5. Genus Taenia
- Life cycle, hosts, stages, transmission, etc.
- Taenia pisiformis (scolex, immature, mature, gravid proglottid)
- Anatomy of mature proglottid
- Taenia eggs: non-operculate, radial lines (striated appearance), thick-shelled
- Cysticercus: cross section + whole mount; invaginated scolex;
6. Genus Echinococcus
- Echinococcus granulosus
- Life cycle, host, transmission, pathology
- Visual id
- Tissue section: unilocular cyst, brood caspules, protoscolices
- Hydatid sand: protoscolices
- Echinococcus multilocularis: multilocular cyst (Why worse?)
7. Family Dilepididae
- General characteristics
8. Dipylidium caninum
- Life cycle, hosts, transmission, etc.
- Double-pored tapeworm!
- Double reproductive system, egg capsules containing many eggs, scolex
9. Family Hymenolepididae
- Life cycle
- Cysticercoid slide in invertebrate Hydra host
- Eggs
10. Order Pseudophyllidae
- General characteristics
11. Diphyllobothrium latum
- Life cycle, transmission, host, stages, etc.
- Pathology
- Scolex: bothria
- Eggs: operculate, contain ciliated embryo (coracidium)
Vocabulary
Monoecious
Dioecious
Endoparasitic
Polyzoic
Scolex
Strobila
Proglottids
Operculum
Coracidium
Strobillation
Metacestode
Cysticercus
Coenurus
Hydatid cyst and sand
Cysticercoid
Evagination
Bothria
Vitellaria
Gravid
Brood capsules
Unilocular cyst
Multilocular cyst
Protoscolex
Procercoid
Plerocercoid