PA11: Intro to helminth parasites

Question 1

Structures of nematodes

Answer 1

Have a cuticle, anus, intestine, pharynx & mouth

Question 2

Structures of trematodes

Answer 2

Have a mouth, uterus, intestine & solid parenchyma

Question 3

Structures of cestodes

Answer 3

Uterus & solid parenchyma

Question 4

Which type of helminth parasite has a blind-ended gut, with a mouth that lets food & waste pass?

Answer 4

Trematodes

Question 5

Which type of helminth parasite has no gut & absorbs nutrients through the cuticle?

Answer 5

Cestodes

Question 6

Which type of helminth parasite has a mouth & anus?

Answer 6

Nematodes

Question 7

Which type(s) of helminth parasite are monoecious?

Answer 7

Trematodes & cestodes

Question 8

Which type(s) of helminth parasite are dioecious?

Answer 8

Nematodes

Question 9

How does the environment affect larval nematodes?

Answer 9

Optimum temperatures between 18-26°C. Optimum humidity 80-100%.
At higher temperatures, development is faster but energy reserves are depleted faster & mortality increases.
No development of larvae < 10°C.

Question 10

What are some survival strategies of nematodes?

Answer 10

Thick-walled eggs to survive longer in the environment.
Retention of L2 cuticle as a sheath on L3 to help with harsh environmental conditions.
Hypobiosis (halted development).
Critical egg hatching requirements allow for mass emergence of larvae in favourable conditions.
Periparturient rise means there are lots of naïve hosts available.

Question 11

What are the 2 types of hypobiosis?

Answer 11

Seasonal or physiological (based on location in tissues).

Question 12

What kind of lifecycles do cestodes have?

Answer 12

Indirect

Question 13

What kind of lifecycles do trematodes have?

Answer 13

Indirect, with a mollusc intermediate.