Chpt 3 - Introduction to Nematodes Flashcards Preview

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Flashcards in Chpt 3 - Introduction to Nematodes Deck (20):
1

The nematode does not utilize an intermediate host

Direct life cycle

Example: Canine hookworm (Ancylostoma spp.):

- develops to the infective third stage in the external environment

- penetrates the dog's skin and migrates to the small intestine, where it matures to an adult

2

The nematode does utilize an intermediate host

Indirect life cycle

Example: Canine heartworm (D. immitis):

- female mosquito ingests microfilariae of canine heartworm with her meal

- female mosquito incubates them

- microfilariae eventually develop into infective third-stage larvae within the proboscis (mouthparts) of mosquito

- when mosquito feeds on uninfected dog, these larvae emerge and migrate into puncture wound

- within dog third-stage larvae molt to fourth-stage larvae, then again to fifth-stage larvae (immature, or preadult, heartworms)

- fifth-stage larvae migrate to dog's right ventricle and pulmonary artery, where they mature to adults

- adults breed and the females produce microfilariae, thus the life cycle begins again

3

The "penis" of a male nematode

Spicules

 

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4

Morphologic feature on the anterior end of an adult nematode

Cervical alae

 

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5

Morphologic feature on the posterior end of a male nematode

Copulatory bursa

 

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6

Fingerlike projections of a copulatory bursa

Bursal rays

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7

Female nematode gives "birth" to live larvae

Larviparous

8

The infective stage of many nematodes

Third-stage larva

9

The shedding of the cuticle ("skin") of a nematode

Molt

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10

Having separate sexes - both male and female nematodes

Dioecious

11

Diagnostically speaking, which reproductive system (male or female) is more important in veterinary practice?

Would you rather use a male nematode or a female nematode for diagnosis of a parasite problem? Why?

Female nematode!

An unrecognized type of nematode can be dissected, and if the nematode is a female, characteristic eggs (or larvae) may be released.

When examined microscopically, these eggs or larvae provide a valuable clue as to the type (or species) of nematode (i.e. different types/species of nematodes have differently shaped eggs/larvae).

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12

Ascaroid, or ascarid, type of nematode eggs

It is best represented by that of Toxocara canis, the canine roundworm

 Adult female nematode producing this egg type is oviparous

This nematode egg contains a single-cell stage within the eggshell

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13

Trichostrongyle, or strongyle, type of nematode eggs

Also known as hookworm

Best represented by that of Ancylostoma caninum, the hookworm of dogs

Adult female nematode producing this egg type is oviparous

This nematode egg contains a morula stage within the eggshell

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14

Spiruroid, or spirurid, type of nematode eggs

Best represented by that of Spirocerca lupi, the esophageal worm of dogs

Adult female nematode producing this egg type is ovoviviparous

This nematode egg contains a first-stage larva within the eggshell

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15

Trichinelloid, or trichuroid, type of nematode eggs

Best represented by that of Trichuris vulpis, the whipworm of dogs

Adult female nematode producing this egg type is oviparous

This nematode egg contains a single-cell stage within the eggshell

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16

External morphologic features used to identify intact adult nematodes

Cuticle

Cervical alae

Copulatory bursa

Bursal rays Spicules

 

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17

Typical nematode life cycle

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18

Infective third stage larva

Infective for the definitive host

19

Which nematodes produce eggs containing a

single-cell stage or a morula stage within the eggshell?

Oviparous nematodes

20

Nematode facts

- Most worm-like of all helminths, mostly free-living forms found in soil

- Elongated, cylindrical, unsegmented worms with tapering ends

- Sexes separate

- Produce eggs (oviparous), larvae (viviparous) or lay eggs containing larvae (ovoviviparous)

- Life cycle has 4 larval stages & the adult form