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BSC Zoology - Parasitology > 02. Helminths > Flashcards

02. Helminths Flashcards

1
Q

Parasitic helminths are always ____-parasites

A

Endoparasites

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2
Q

Why does harbouring a parasite affect the host?

A

Disrupts the nutrient uptake

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3
Q

Name mechanisms of survival that have evolved in parasitic helminths

A

immune evasion

immunological masking mechanisms

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4
Q

What are the ways that helminths injure their hosts?

A
  • Mechanical means

- Chemical means

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5
Q

What is an example of a helminth that causes obstruction of the intestine?

A
  • Ascaris lumbricoides

- Dog heartworm does a similar thing - blocks the heart

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6
Q

Name the categories of parasitic helminths

A
  • Cestodes (Tapeworms)
  • Trematodes (Flukes)
  • Nematodes (Roundworms)
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7
Q

What is the shape of cestodes?

A

segmented and plane (flat)

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8
Q

Do cestodes have a body cavity?

A

NO

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9
Q

What is the body covering of a cestode?

A

Tegument (for absorption as well as classic functions)

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10
Q

Do cestodes have a digestive tube?

A

NO

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11
Q

Which parasitic helminths are hermaphrodites?

A
  • Cestodes

- Trematodes (with the exception of Schisto, which are dioecious)

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12
Q

What category of parasitic helminth are Schistosomas?

A

Trematodes

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13
Q

What is the sexual morphology of Schistosomes?

A

Dioecious

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14
Q

What are the organs for attachment to the host in cestodes?

A
  • Sucker (or bothridia)

- and some have a rostellum with hooks

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15
Q

What is the shape of trematodes?

A

Unsegmented and plane (flat)

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16
Q

Do trematodes have a body cavity?

A

NO

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17
Q

What is the body covering of a trematode?

A

Tegument

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18
Q

Do trematodes have a digestive tube?

A

Yes, but it is incomplete. it ends in the cecum (i.e. they have only an oral opening/not a complete gut)

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19
Q

What is the sexual morphology of trematodes?

A

Hermaphrotitic, except Schisto

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20
Q

What are the organs for attachment to the host in trematodes?

A
  • Oral sucker

- Ventral sucker (acetalbulum)

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21
Q

What is the shape of nematodes?

A

Unsegmented, cylindrical (round)

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22
Q

Do nematodes have a body cavity?

A

YES

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23
Q

What is the body covering of a nematode?

A

Cuticle

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24
Q

Do nematodes have a digestive tube?

A

Yes, and it is complete - ends in anus.

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25
Q

What is the sexual morphology of nematodes?

A

Dioecious

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26
Q

What are the organs for attachment to the host in nematodes?

A
  • Lips
  • Teeth
  • Filariform extrematies
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27
Q

Name some cestoda species

A
  • Taena saginata
  • Taena solium
  • Hymenolepsis nana
  • Hymenolepsis diminuta
  • Echinococcus granulosis
  • Diphyllobothrium
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28
Q

What is the site of infection for most cestodes?

A

Small intestine

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29
Q

Which cestode(s) is/are found in Argentina, Europe, Japan, Siberia, Great lakes area USA and Canada?

A

Diphyllobothrium

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30
Q

What is the phylum of class cestoda?

A

Platyhelminthes

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31
Q

What are the two subclasses of class cestoda?

A
  • Subclass Cestodaria

- Sunclass Eucestoda

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32
Q

What is found in Subclass Eucestoda?

A

Tapeworms

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33
Q

What is the function of the suckers on cestodes?

A

Attachment, NOT for feeding

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34
Q

Each proglottid has a complete set of ______.

A

Male and female reproductive organs

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35
Q

What makes the life style of cestodes SIMPLE?

A

There are no asexual phases

36
Q

What makes the life style of cestodes COMPLEX

A

At least one intermediate host is required as well as the definitive host

37
Q

Name the various stages of the life cycle of cestodes

A
  • Eggs
  • Oncosphere
  • Cysticercoid/cysticercus
  • Coracidium (dont need to know)
  • Procercoid (dont need to know)
  • Plerocercoid (dont need to know)
  • Adult
38
Q

What types of animals can be the intermediate host of a parasitic helminth?

A
  • Mammal
  • Arthropod
  • Fish
  • Bird
  • Reptile
39
Q

What is the dwarf tapeworm?

A

Hymenolepis nana

40
Q

What is the beef tapeworm? (intermediate is the cow)

A

Taenia saginata

41
Q

What is the worm that has a pig intermediate?

A

Taenia solium

42
Q

What is the fish tapeworm?

A

Diphyllobothrium latum

43
Q

What is/are the intermediate(s) of the fish tapeworm? (Diphyllobothrium latum)

A
  • First intermediate is a copepod

- Then it is a freshwater fish

44
Q

What are the 3 distinct regions of tapeworms?

A
  • Scolex
  • Neck
  • Strobila
45
Q

What does the strobila consist of?

A

Proglottids

46
Q

What are the 3 stages that proglottids are characterized in?

A
  • Immature
  • Mature
  • Gravid
47
Q

Do cestodes have a mouth?

A

NO

48
Q

What are the two important orders of class cestoda?

A
  • Order pseudophyllidea

- Order cyclophyllidea

49
Q

Which order contains slit-like suckers or grooves on their scolex? what are they called?

A
  • Pseudophyllidea

- Bothridia

50
Q

Which order contains 4 suckers and sometimes hooks on their scolex?

A

Cyclophillydea

51
Q

What can be used to identify tapeworms?

A

The scolex

52
Q

What is the undifferentiated/unsegmented region between the scolex and the strobila of a cestode?

A

The neck

53
Q

What is the function of the neck on a cestode?

A

Contains stem cells that are responsible for giving rise to new proglottids, the older ones move posteriorly to make way for the new ones

54
Q

What is the strobila?

A
  • The most posterior of the 3 distinct regions on a cestode

- It is a linear series of segments of proglottids

55
Q

What are the immature proglottids?

A
  • They are newly formed

- They do not yet contain sex organs

56
Q

What are mature proglottids?

A

They contain both male and female sex organs

57
Q

What are gravid proglottids?

A
  • They develop after mating occurs

- They contain hundreds to thousands of embryonated eggs

58
Q

What develops first, the male or female reproductive system?

A

Male

59
Q

What are the structures of the male reproductive system?

A
  • Many testes (3-100s, depending on species)
  • Vasa efferentia
  • Vas deferens (often highly coiled)
  • Cirrus sac with cirrus
  • Common genital pore
60
Q

What are the structures of the female reproductive system?

A
  • Ovaries
  • Vitellaria
  • Mehlis’s gland
  • Uterus - contains eggs in branches
  • Vagina
  • Common genital pore
61
Q

What happens to the female and male organs in gravid proglottids?

A
  • The male organs dissapear

- Most of the female organs dissapear except for the egg-filled uterus

62
Q

Which proglottids will mate?

A

Mature proglottids in proximity - can be from the same strobila of another if there are multiple worms in the infecton

63
Q

How are the eggs transmitted? (two different ways that result in the same fecal-oral route of transmission)

A

Two possible ways

  • The proglottid disintegrates and eggs are released in host feces
  • The whole proglottid, containing the embryonated eggs, is released
64
Q

What do the eggs contain? What is that called?

A

Hexacanth larva - called an oncosphere (life cycle stage)

65
Q

What are the layers of the cestode egg from inside to out?

A
  • Oncosphere (hexacanth larva)
  • Inner envelope
  • Ciliated embryophore
  • Outer envelope
  • Shell
66
Q

What is the operculum and which genus has this?

A
  • It is like a lid to release the larvae rather than the shells disintegrating
  • Diphyllobothrium
67
Q

Which genus does NOT have a shell on their eggs?

A

Taenia

68
Q

Which genus has all the layers of the egg but no operculum?

A

Hymenolepsis

69
Q

What is the tegument?

A

The external surface of a cestode

70
Q

What is the function of a tegument on cestodes?

A
  • protection
  • locomotion
  • sensory surface
  • more notably; a layer to take up nutrients and through which secretions and excretions can pass
71
Q

How does the tegument help the parasite survive in the host?

A

It is resistant to attack from digestive enzymes and immune responses

72
Q

What is the glycocalyx?

A

a layer of carbohydrate-containing molecules covering the entire surface of the tegument

73
Q

What are the purposes of the glyxocalyx?

A
  • Protecting the parasite from host digestive enzymes
  • Enhancing nutrient absorption
  • Maintaining the parasite’s surface membrane
74
Q

What is the purpose of the microvilli

A

They increase the surface area of the tapeworm ~ 20X

75
Q

What are the two layers of the tegument?

A
  • Syntegument

- Cytotegument

76
Q

What composes the syntegument?

A

It is the outer, anucleate, synctial cytoplasmic layer containing mitochondria and secondary bodies

  • has dense granules
  • circular and longitudinal muscle
77
Q

What composes the cytotegument?

A

Nucleated cell bodies lying beneath the tegumental muscles and connected to the syntegument
- Nucleus and mitochindria

78
Q

What kind of compounds do the cestodes absorb?

A
  • Low molecular weight compounds
  • They do not produce digestive enzymes and they rely on the host to breakdown high molecular weight compounds into low MW
79
Q

What are the two pairs of excretory canals?

A
  • Ventrolateral

- Dorsolateral

80
Q

What are osmoconformers

A

they absorb and reduce absorption of water depending on the tonicity of the medium - little ability to regulate their body volume on their own

81
Q

What is the main nerve center of a cestode?

A

the scolex

82
Q

Pork tapeworm

A

Taenia solium

83
Q

Beef tapeworm

A

Taenia saginata

84
Q

Fish tapeworm

A

Diphyllobothrium latum

85
Q

Dwarf tapeworm

A

Hymenolepis nana

86
Q

Rat tapeworm

A

Hymenolepis diminuta

87
Q

Dog tapeworm

A

Diphylidium caninum

BSC Zoology - Parasitology (27 decks)

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