Ectoparasites Flashcards
What is an ectoparasite?
parasite that lives on the outside of host but not within the body
What are some examples of ectoparasites?
Mostly arthropods:
- Fleas
- Lice
- Ticks
- Mites
- Copepods
- Flies
- Bed bugs
But can also be
- Leeches
- Vampire bats
- Lampreys
Name some examples of negative effects on hosts
- Anaemia
- Detrimental immune reactions
- Irritability
- Dermatitis, skin necrosis
- Low weight gains
- Secondary infection
- Focal haemorrhages
- Blockage of orifices
- Pathogen transmission
What evidence is there in the fossil record that suggests the existence of ectoparasites?
Glyptodonts = extinct relatives of armadillos
- white and blue damage to ornamental osteoderm by fleas on males after comparison with flea damage today
Describe the life cycle of a tick
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
What disease do ticks carry, how is transmitted and how fatal is it?
Lyme disease- transmitted via bite of various ticks of genus lxodes found in Northern hemisphere
- Debilitating by rarely fatal- can be treated with antibiotics
Why are lice hard to eradicate?
Due to overlapping generations
Describe the life-cycle of a louse
- Mature adult female lays eggs
- 2nd gen nymphs hatch and mature rapidly and can reproduce at same time of 1st reproducing females
What gender is more likely to get lice and why?
Females due to long hair and more likely to be in closer contact
How do lice spread from host to host?
Close contact- cannot live off of body
Name the types of lice humans host and what do they all have in common?
Pediculus humanus capitis = head lice
Pediculus humanus humanus = body lice
Pthirus pubis = pubic lice
= all suck blood and infest hair areas or clothing
What are the differences among the types of lice humans host?
- 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
What do lice tell us about evolution of human body hair ?
- Pubic lice were general body lice on gorillas, but switched hosts to humans 3mya through sharing contact
- 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
When looking at a louse genome, what can be discovered?
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
Why are body lice threatened?
Modern hygiene and clothes washing technology
Describe an example of an ecological effect of parasites
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:
- 1826- Wellington ship dropped off stale water casks containing mosquito larvae
- Introduced mosquitoes fed on native birds
- 1900- people moved there and brought livestock- chickens brought avian pox virus which started killing birds
- 1920s- people replaced missing birds with new species
- Imports brought avian malaria and was spread by competent mosquitoes
- 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
Define: arms race and what is the goal for each side?
= conflict between 2 parties
GOAL = to maxamise defensive capability to frighten opposition into submission
What does an arms race result in?
Rapid escalation in the amount/complexity of weaponry on both sides
Describe an example of an ecological arms race
Coevolution between hosts and parasites:
- Host-parasite interactions = frequency dependent
- Parasites adapt to most common host type
- Rare less suitable hosts have a survival and therefore reproductive advantage, until they reproduce so successfully that they become the most common host type
- Parasites adapt to them as their main host due to more reproductive opportunities
= red queen effect
What is a frequency-dependent interaction?
How common a parasite can be in a population depends on how common their favourite host is
What is the red queen effect?
Sexual reproduction results in genetic recombination
= just enough variation to keep some individuals ahead of parasites
Where is the evidence for the red queen effect?
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
define: obligate
= only method of reproduction available
