Ectoparasites

Question 1

What is an ectoparasite?

Answer 1

parasite that lives on the outside of host but not within the body

Question 2

What are some examples of ectoparasites?

Answer 2

Mostly arthropods:
- Fleas
- Lice
- Ticks
- Mites
- Copepods
- Flies
- Bed bugs

But can also be
- Leeches
- Vampire bats
- Lampreys

Question 3

Name some examples of negative effects on hosts

Answer 3

• Anaemia
• Detrimental immune reactions
• Irritability
• Dermatitis, skin necrosis
• Low weight gains
• Secondary infection
• Focal haemorrhages
• Blockage of orifices
• Pathogen transmission

Question 4

What evidence is there in the fossil record that suggests the existence of ectoparasites?

Answer 4

Glyptodonts = extinct relatives of armadillos
- white and blue damage to ornamental osteoderm by fleas on males after comparison with flea damage today

Question 5

Describe the life cycle of a tick

Answer 5

3 host system- go up in size as larvae developand become larger:
1. small mammal
2. intermediate mammal
3. Large mammal
- each feed from host triggers next developmental stage of tick and spread infection

Question 6

What disease do ticks carry, how is transmitted and how fatal is it?

Answer 6

Lyme disease- transmitted via bite of various ticks of genus lxodes found in Northern hemisphere
- Debilitating by rarely fatal- can be treated with antibiotics

Question 7

Why are lice hard to eradicate?

Answer 7

Due to overlapping generations

Question 8

Describe the life-cycle of a louse

Answer 8

1. Mature adult female lays eggs
2. 2nd gen nymphs hatch and mature rapidly and can reproduce at same time of 1st reproducing females

Question 9

What gender is more likely to get lice and why?

Answer 9

Females due to long hair and more likely to be in closer contact

Question 10

How do lice spread from host to host?

Answer 10

Close contact- cannot live off of body

Question 11

Name the types of lice humans host and what do they all have in common?

Answer 11

Pediculus humanus capitis = head lice
Pediculus humanus humanus = body lice
Pthirus pubis = pubic lice

= all suck blood and infest hair areas or clothing

Question 12

What are the differences among the types of lice humans host?

Answer 12

• head lice- have tarsal hooks adapted for clinging to fine head hair
• Pubic lice- adapted for coarser hair and more moist parts of body
• Body lice- live in clothing and commute to skin to feed, but do not live on body

Question 13

What do lice tell us about evolution of human body hair ?

Answer 13

1. Pubic lice were general body lice on gorillas, but switched hosts to humans 3mya through sharing contact
2. Human body hair lost = pubic lice trapped in pubic region

• so by timing of divergence of lice species- estimates can be made about milestones in human history like the loss of body hair

Question 14

When looking at a louse genome, what can be discovered?

Answer 14

can inform host history:
- body lice branched off from head lice 190000 years ago = when humans started wearing clothes- so certain species of lice took advantage of this and lived in clothes and communted to body

Question 15

Why are body lice threatened?

Answer 15

Modern hygiene and clothes washing technology

Question 16

Describe an example of an ecological effect of parasites

Answer 16

Avian Malaria in Hawaii = very isolated:
- Lots of endemic birds due to evolving in isolation overtime

e.g. Honeycreeper feed on nectar and have a range of bill shapes to suit different flowers that they feed on:

1. 1826- Wellington ship dropped off stale water casks containing mosquito larvae
2. Introduced mosquitoes fed on native birds
3. 1900- people moved there and brought livestock- chickens brought avian pox virus which started killing birds
4. 1920s- people replaced missing birds with new species
5. Imports brought avian malaria and was spread by competent mosquitoes
6. 1940s- malaria was killing native birds on every island

Results =
- High altitude birds found refuge
- Low altitude birds were wiped out and replaced
- Some evolved resistance and began to recolonise lower altitudes like the Amakihi
- Some were lost forever like Po’ouli

= Due to climate change, avian malaria is increasing again

Question 17

Define: arms race and what is the goal for each side?

Answer 17

= conflict between 2 parties
GOAL = to maxamise defensive capability to frighten opposition into submission

Question 18

What does an arms race result in?

Answer 18

Rapid escalation in the amount/complexity of weaponry on both sides

Question 19

Describe an example of an ecological arms race

Answer 19

Coevolution between hosts and parasites:

1. Host-parasite interactions = frequency dependent
2. Parasites adapt to most common host type
3. Rare less suitable hosts have a survival and therefore reproductive advantage, until they reproduce so successfully that they become the most common host type
4. Parasites adapt to them as their main host due to more reproductive opportunities

= red queen effect

Question 20

What is a frequency-dependent interaction?

Answer 20

How common a parasite can be in a population depends on how common their favourite host is

Question 21

What is the red queen effect?

Answer 21

Sexual reproduction results in genetic recombination
= just enough variation to keep some individuals ahead of parasites

Question 22

Where is the evidence for the red queen effect?

Answer 22

Potamopyrgus antipodarum = snail species that can be sexual or asexual:
- Parasitised by several species of flukes that eat their gonads
- Snail populations consist of:
Males
Obligate sexual females (producing male and female offspring)
Obligate asexual females- daughter clones no variety

RESULTS =
populations with higher prevalence of parasite had higher proportion of males and sexual females

Question 23

define: obligate

Answer 23

= only method of reproduction available