Biology: Tapeworms and Cestodes
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Questions and Answers

What is the primary function of the tegument in cestodes?

  • To aid in reproduction
  • To facilitate movement
  • To absorb nutrients directly (correct)
  • To regulate body temperature
  • What is characteristic of the nervous system of cestodes?

  • It has a complex brain structure
  • It has a cerebral ganglion in the scolex (correct)
  • It is decentralized with no central nerve center
  • It is highly developed for sensory perception
  • What is unique about the reproductive system of true tapeworms?

  • They are dioecious, with separate sexes
  • They have a complex reproductive cycle
  • They have a single reproductive system
  • They are hermaphrodites, with both male and female reproductive systems (correct)
  • What type of excretory system do cestodes have?

    <p>Protonephridial flame bulb system</p> Signup and view all the answers

    What is the function of microvilli in the excretory ducts of cestodes?

    <p>To regulate ionic concentrations of the excretory fluid</p> Signup and view all the answers

    What is characteristic of operated eggs of cestodes?

    <p>They are immature when voided to the external environment</p> Signup and view all the answers

    What is a characteristic of microtriches?

    <p>They are specialized microvilli covering the surface of the tegument</p> Signup and view all the answers

    What is the common external opening for both male and female reproductive systems in cestodes?

    <p>Genital pore</p> Signup and view all the answers

    What is the mode of infection of Diphyllobothrium latum?

    <p>Ingestion of improperly cooked or smoked fish infected with Larva</p> Signup and view all the answers

    What is the clinical feature of heavy Diphyllobothrium latum infection?

    <p>Anemia and neurological problems associated with vitamin B12 deficiency</p> Signup and view all the answers

    What is the shape of the egg of Diphyllobothrium latum?

    <p>Broadly ovoid</p> Signup and view all the answers

    What is the characteristic feature of the scolex of Spirometra mansoni?

    <p>It has two sucking grooves</p> Signup and view all the answers

    What is the size of the egg of Spirometra mansoni?

    <p>52-78 µm ×31-44 µm</p> Signup and view all the answers

    What is the second intermediate host of Spirometra mansoni?

    <p>Frog</p> Signup and view all the answers

    What is the mode of infection of Spirometra mansoni?

    <p>Drinking water contaminated with infected copepods</p> Signup and view all the answers

    What is the infective stage of Spirometra mansoni?

    <p>Plerocercoid / Sparganum</p> Signup and view all the answers

    What is a characteristic feature of the scolex of Cysticercus?

    <p>It has four cup-like round suckers</p> Signup and view all the answers

    What is the characteristic of the eggs of Cysticercus?

    <p>They are not operculated and can develop only in the intermediate host</p> Signup and view all the answers

    How many intermediate hosts are involved in the larval development of Cysticercus?

    <p>One</p> Signup and view all the answers

    What is the characteristic of the vitelline glands of Cyclophyllidea?

    <p>They are concentrated in a single mass</p> Signup and view all the answers

    What is the characteristic of the genital pore of Pseudophyllidea?

    <p>It is on the ventral surface of the segment</p> Signup and view all the answers

    What is the characteristic of the oncosphere of Cyclophyllidea?

    <p>It is never a ciliated embryo</p> Signup and view all the answers

    Which of the following is NOT a species belonging to the Order Cyclophyllidea?

    <p>Diphyllobothrium latum</p> Signup and view all the answers

    What is the common name of the parasite Diphyllobothrium latum?

    <p>Fish tapeworm</p> Signup and view all the answers

    What is the characteristic of the scolex of Diphyllobothrium latum?

    <p>It has longitudinal slits</p> Signup and view all the answers

    What is the size of the adult Diphyllobothrium latum?

    <p>10m or more</p> Signup and view all the answers

    What is the intermediate host of Diphyllobothrium latum?

    <p>Cyclops or diatomes</p> Signup and view all the answers

    What is the definitive host of Diphyllobothrium latum?

    <p>Humans</p> Signup and view all the answers

    Where is Diphyllobothrium latum commonly found?

    <p>Widely distributed in lake areas of Europe, Asia, Far East, North America, South America, and Central Africa</p> Signup and view all the answers

    What is the color of the adult Diphyllobothrium latum?

    <p>Grayish-yellow</p> Signup and view all the answers

    What is the primary way to avoid sparganosis?

    <p>Drinking only safe water</p> Signup and view all the answers

    What is the most common localization of sparganum in human?

    <p>Subcutaneous connective tissue and superficial muscles</p> Signup and view all the answers

    What is the clinical manifestation of cerebral sparganosis?

    <p>Seizures, headache, and focal neurological signs</p> Signup and view all the answers

    What is the treatment for sparganosis?

    <p>Surgical removal of the nodular lesion</p> Signup and view all the answers

    What is the primary method of diagnosis for sparganosis?

    <p>Removing the nodular lesion and confirming the presence of sparganum</p> Signup and view all the answers

    What is the common practice in Vietnam, Thailand, and parts of China that is responsible for ocular sparganosis?

    <p>Applying frog or snake flesh as poultice on the eye or wound</p> Signup and view all the answers

    What is the type of sparganosis characterized by nodules in the oral mucosa?

    <p>Oral sparganosis</p> Signup and view all the answers

    What is the type of sparganosis characterized by seizures, headache, and focal neurological signs?

    <p>Cerebral sparganosis</p> Signup and view all the answers

    Study Notes

    Cestodes (Tapeworms)

    • Lack a digestive system and absorb nutrients through their tegument.
    • No digestive tract; absorb all nutrients directly through the tegument.

    Tegument

    • Syncitium: cytons connected by trabeculae (cytoplasmic bridges) to distal cytoplasm.
    • Microtriches (singular microtrix): highly specialized microvilli covering the entire surface of the tegument of cestodes.

    Nervous and Sensory System

    • Main nerve centre: cerebral ganglion in the scolex.
    • Motor and sensory innervation depends on the number and complexity of the scolex.
    • Smaller nerves emanate from the commissures to supply the general body muscular and sensory endings.

    Reproduction

    • True tapeworms are exclusively hermaphrodites (Dioecious): have both male and female reproductive systems in their bodies.
    • Reproductive system includes one or many testes, cirrus, vas deferens, and seminal vesicle as male organs, and a single lobed or unlobed ovary with the connecting oviduct and uterus as female organs.

    Excretion and Osmoregulation

    • Cestodes have the protonephridial flame bulb system typical of flatworms.
    • Flame cell protonephridium embedded throughout the parenchyma.
    • Excretory ducts are lined with microvilli involved in transport of excretory wastes and may help to regulate ionic concentrations of the excretory fluid.

    Developmental Stages of Cestodes

    • Egg: two types - Operculated and Non-operculated.
    • Larvae: two types - Solid (e.g., Procercoid, Plerocercoid) and Cystic (true bladder) with single scolex (e.g., Cysticercus) or many scolexes and/or daughter cysts (e.g., Hydatid cyst, Coenurus cyst).

    Order Cyclophyllidea Characteristics

    • Large or small worms consisting of chains of segments.
    • Scolex is quadrate with four cup-like round suckers.
    • An apical rostellum with hooklets may be present.
    • Vitelline glands concentrated in a single mass.
    • Common genital pore is marginal (on lateral side of segment).
    • No uterine opening for the exit of eggs from the gravid uterus.
    • Eggs only escape from the rupture or disintegration of ripe segments.

    Order Pseudophyllidea Characteristics

    • Large worms consisting of a long chain of segments.
    • Scolex has two slit-like sucking grooves (bothria) instead of suckers.
    • Vitelline glands are widely scattered in the parenchyma and composed of many acini.
    • Genital pores are on the ventral surface of the segment and are not marginal.
    • Uterus opens to the exterior through which eggs come out.
    • Eggs are operculated and can develop only in water; immature when oviposited (unembryonated) and oncosphere gives rise to ciliated embryo.

    Classification

    • Order Cyclophyllidea: less medically important, includes Taenia saginata, Taenia solium, Hymenolepis spp., Echinococcus granulosus, and Echinococcus multilocularis.
    • Order Pseudophyllidea: includes Diphyllobothrium latum and Spirometra spp.

    Life Cycle of Cestodes

    • Adult in definitive host.
    • Egg: operculated or non-operculated.
    • Coracidium: ciliated embryo stage.
    • Oncosphere: immature embryo stage.
    • Solid larval form: procercoid larva.
    • Cystic larval form: plerocercoid larva, cysticercus, coenurus, hydatid cyst, etc.

    Diphyllobothrium latum

    • Common name: Fish tapeworm.
    • Order Pseudophyllidea.
    • Adult: the largest tapeworm, up to 10m or more in length, grayish-yellow in color.
    • Scolex is elongated, spoon-shaped, with longitudinal slits (bothria) and no rostellum and hooklets.
    • Habitat: small intestine.
    • Hosts: definitive host - human; reserve host - fish-eating animals; primary intermediate host - Cyclops or diatoms; secondary intermediate host - freshwater fish.
    • Mode of infection: ingestion of improperly cooked or smoked fish infected with plerocercoid larvae.
    • Clinical features and pathology: abdominal discomfort, loss of weight, loss of appetite, and some malnutrition; anemia and neurological problems associated with vitamin B12 deficiency in heavily infected individuals.

    Spirometra mansoni

    • Order Pseudophyllidea.
    • Morphology: adult worm measures 60-100 cm in length; scolex is elongated and spoon-shaped with two sucking grooves.
    • Egg: 52-78 µm × 31-44 µm, light yellow in color, operculated.
    • Plerocercoid/Sparganum: tape-like, unsegmented body, white in color, infective stage.
    • Definitive host: dog, cat, etc.
    • 1st intermediate host: freshwater copepod.
    • 2nd intermediate host: frog.
    • Transport (paratenic/transfer) host: snake, bird, mammal.
    • Mode of infection: drinking contaminated water, eating raw or undercooked meat of infected animals, or through larval transfer (applying flesh as a poultice on the eye or wound).
    • Pathogenesis and clinical features: sparganosis in humans is a tissue infection caused by plerocercoid; can cause ocular, subcutaneous, oral, and cerebral sparganosis.

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    Description

    This quiz covers the biology of tapeworms and cestodes, including their unique features and characteristics such as the lack of a digestive system and the presence of microtriches.

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