Order Rhabditida: Strongyloides

Question 1

The tissue phase is a developmental requirement following the
evolutionary loss of skin penetration or intermediate hosts.

Answer 1

Nematode migration

Question 2

T/F. migration is a selectively advantageous life-history strategy.

Answer 2

True

Question 3

T/F. taxa exploiting tissue habitats during development are, on average, smaller than their closest relatives that develop wholly in the gastrointestinal tract

Answer 3

False. bigger than their closest relatives

Question 4

T/F. Time to reproduction is the same, indicating that worms with a tissue
phase during development grow faster

Answer 4

True

Question 5

small worms
often with six lips (primitive condition)
usually with a conical tail
most species inhabit decaying vegetation or other
organic matter

Answer 5

Order Rhabditida

Question 6

facultatively parasitic
many are parthenogenic or hermaphroditic if parasitic
up to two dozen different families
Humans are the principal host
dogs, cats and other mammals as reservoir hosts

Answer 6

Order Rhabditida

Question 7

Enteral circulation (endoautoinfection) or
perianal skin (exoautoinfection).

Answer 7

Strongyloides stercoralis

Question 8

Rhabditiform Larva:
225 μm by 16 μm

elongated
esophagus with a
pyriform posterior bulb

slightly smaller and less
attenuated posteriorly

shorter
buccal capsule and a
larger genital primordium

Answer 8

Strongyloides stercoralis
(threadworm)

Question 9

Filariform Larva:
infective but nonfeeding stage

Slender, about 550 μm
in length

smaller than hookworm
filariform larva

with a distinct cleft
(notched) at the tip of
the tail

Answer 9

Strongyloides stercoralis

Question 10

Swollen baby syndrome

Answer 10

Autoinfection of strongyloides stercoralis