10. Nematodes intro

Question 1

nematodes make up what fraction of the multicellular animals on earth?

Answer 1

4/5

Question 2

how many species of nematodes have been described?

Answer 2

500,000

Question 3

what is a non-parasitic nematode that is used for research and development?

Answer 3

Caenorhabditis elegans (C. elegans)

Question 4

what is the most common human parasitic nematode worldwide?

Answer 4

Acaris lumbricoides

Question 5

what is the most common human parasitic nematode in US/Canada?

Answer 5

Enterobius vermicularis

Question 6

in most species _____ reproduction by adult nematodes is the norm and occurs within an infective definitive host

Answer 6

sexual

Question 7

what are the ways in which the larval stages may be passed?

Answer 7

• within the egg
• free living in soil
• parasitic in an intermediate host
• parasitic in the definitive host

Question 8

what is the basic life cycle of nematodes

Answer 8

• egg
• four larval stages (L1, L2, L3, and L4)
• two adult stages comprising separate males and females

Question 9

what is L5?

Answer 9

another name for sexually immature adults

Question 10

what are the two phases of the life cycle of nematodes?

Answer 10

• pre-parasitic

- parasitic

Question 11

what stages are part of the pre-parasitic phase?

Answer 11

• L1, L2 and L3

- the parasite must pass through these stages before the nematode is again infective for another host

Question 12

what stages are part of the parasitic phase?

Answer 12

• L3 and onward

- will undergo a migration within the body of the definitive host

Question 13

which nematodes have infectious eggs?

Answer 13

• ascaris (ex: ascaris lumbricoides)

- pinworm (ex: enterobius vermicularis)

Question 14

which nematode is up to 30 cm in length and lives in the intestines of humans, horses, and pigs?

Answer 14

Ascaris

Question 15

which nematode spends the entire lifecycle in or on the human host?

Answer 15

pinworm/Enterobius vermicularis

Question 16

which parasite lays eggs in the perianal region causing itch?

Answer 16

pinworm/Enterobius vermicularis

Question 17

which nematodes have infectious larvae?

Answer 17

• adult hookworm (Necator americanus)

- trichina worm (Trichinella spiralis)

Question 18

how do the larvae of the hookworm enter the human host?

Answer 18

by penetrating skin

Question 19

describe the path in the body which is taken by the hookworm?

Answer 19

they penetrate the skin, enter the blood stream to travel to the lungs and are coughed up and swallowed in the sputum

Question 20

what is the best way to avoid getting hookworm?

Answer 20

wearing shoes

Question 21

what is the largest nematode and in what animal is it found?

Answer 21

• Placentonema gigantisma
• 9-13m long
• found in sperm whales

Question 22

is the body of a nematode segmented or non segmented? flat or round?

Answer 22

• non-segmented

- round (roundworm) and tapered at both ends

Question 23

what does the nematode body wall consist of?

Answer 23

• an outermost cuticle

- an underlying hypodermis that secretes the cuticle

Question 24

what is the cuticle made of?

Answer 24

• the syncytial hypodermis secretes the thick outer layer of collagen
• it is proteinaceous (not callagen) with outer lipid laters

Question 25

what are the characteristics of the collagenous cuticle?

Answer 25

- tough | - flexible

Question 26

does a nematodes cuticle have cilia?

Answer 26

no

Question 27

how often is the cuticle molted/shed?

Answer 27

usually four times in the life of the nematode, as it goes through the life stages

Question 28

with which other groups does the nematode share the characteristics of a molted cuticle and the lack of cilia?

Answer 28

- arthropods | - ecdysozoans

Question 29

what constrains the growth of the parasite between life stages?

Answer 29

the cuticle

Question 30

what are the two steps of molting?

Answer 30

- SYNTHESIS of a new cuticle by the hypodermis - EXSHEATHMENT - a process by which the old cuticle is loosened and ruptured followed by the larva wriggling out of the casing

Question 31

what does exsheathment initiate?

Answer 31

infection

Question 32

the process of exsheathment during infection is not only _______ but is also _______ within the host

Answer 32

- host-specific | - site-specific

Question 33

what kind of muscle lies below the hypodermis?

Answer 33

longitudinal muscle (NO circular muscle, meaning the worm cannot shorten and lengthen as do earthworms)

Question 34

movement of the parasite is due to _________ caused by contraction of the longitudinal muscles

Answer 34

undulating motion

Question 35

what type of motion is observed with longitudinal muscle?

Answer 35

dorsoventral flexion, which allows for the characteristic sinusoidal undulating motion

Question 36

what is another name for the body cavity?

Answer 36

pseudocoelom

Question 37

why is it a pseudocoelom and not a coelom?

Answer 37

it is not lined internally with cilia

Question 38

what fills the pseudocoelom?

Answer 38

pseudocoelomic fluid

Question 39

where are reproductive organs found?

Answer 39

suspended in the pseudocoelom

Question 40

what are the two functions of the pseudocoelomic fluid?

Answer 40

- gives the body rigidity | - transports materials from cell to cell

Question 41

is the digestive tract complete or incomplete?

Answer 41

complete

Question 42

what are the parts of the digestive tract in order?

Answer 42

mouth --> pharynx --> oesophagus --> intestine --> anus

Question 43

what is found in the intestine to increase absorption?

Answer 43

microvilli

Question 44

who does most of the digestion, the host or the nematode?

Answer 44

the host, the nematode mostly just absorbed the digested food of the host

Question 45

what does the nervous system of the nematode consist of?

Answer 45

- a ganglian nervous system - with an anterior neural ring, - and 2 or 4 longitudinal nerve truncs extending the length of the nematode

Question 46

what is another name for the anterial neural ring?

Answer 46

circumesophageal ring

Question 47

where is the excretory pore of the nematode?

Answer 47

near the mouth

Question 48

what are the characteristics of the excretory system?

Answer 48

- simple and tubular - one or 2 one-celled renette glands and excretory ducts - excretory pore is anterior - NO flame cells*

Question 49

does the nematode have a respiratory system?

Answer 49

no

Question 50

how does gas exchange occur in nematode?

Answer 50

diffusion

Question 51

all nematodes are ______ (reproductive anatomy)

Answer 51

dioecious (separate male and female organisms)

Question 52

what does the reproductive system consist of?

Answer 52

tubular organs lying in the pseudocoelom

Question 53

what do all nematodes release?

Answer 53

eggs

Question 54

which are smaller, male or female nematodes?

Answer 54

male

Question 55

what is particular about the posterior end of a male nematode?

Answer 55

it is curved

Question 56

what does the male reproductive system consist of?

Answer 56

a single tubules starting with one testis and ending with a terminal cloaca and copulatory spicules

Question 57

what is different in the female reproductive system?

Answer 57

the organs are doubled

Question 58

what are the components of the female reproductive system?

Answer 58

- 2 threadlike ovaries - 2 oviducts - 2 uterus - single genital pore at mid-body

Question 59

what is common about the male and female reproductive organs?

Answer 59

they are both tubular and continuous, and increase in diameter as they extend to the genital opening