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BIO220 > BIO220 Lecture 11 > Flashcards

BIO220 Lecture 11 Flashcards

Parasite extended phenotypes

1
Q

What is a phenotype?

A

Any observable characteristic or trait of an organsim

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2
Q

Phenotype is determined by… (standard view)

A

Genotype and environment

Z = G + E

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3
Q

Who came up with the notion of extending phenotype outside the cell?

A

Dawkins

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4
Q

What does extending phenotype mean?

A
  1. Things produced by individuals
  2. Things produced by several individuals
  3. Things produced in other individuals
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5
Q

Example of extended phenotype: things produced by a individual

A

Bower nest (blue items):

  • subject to genetic & environmental variation
  • influences fitness
  • subject to selection
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6
Q

Example of extended phenotype: things produced by several individual

A

Beaver dam building:

- gene encodes for building taller dams

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7
Q

Example of extended phenotype: things produced in other individuals

A

Parasites manipulate host behaviour

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8
Q

Explain why things produced in other individuals is also a part of this individual’s phenotype

A

Dawkins: an individual’s behaviour will maximize survival of the genes corresponding to that behaviour, whether or not those genes happen to be in the body of the individual performing the behaviour.

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9
Q

3 categories of exteneded phenotypes exhibited by parasites

A
  1. Behavioural modification
  2. Morphological modification
  3. Molecular modification
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10
Q

Examples of behavioural modification by the parasite (7)

A
  1. Increase host risk taking & aggression (rabies, toxoplasmosis)
  2. Increase vector biting rate (malaria)
  3. Modify vector feeding preferences (malaria)
  4. Alter host micro habitat preference (cockroach)
  5. Death grip (ant)
  6. Cocoon web construction (spider)
  7. Host suicide (horsehair worm in crickets)
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11
Q

Parasite increase host risk taking & aggression

A

Rabies & toxoplasmosis:

Increase transmission to new host

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12
Q

Toxoplasmosis

A

Disease transmitted through cat poop.
Ideal host: cat gut
Intermediate host: mice

Infected mice will go towards cat; more likely to be eaten by cat so pathogen can end up in cat gut.

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13
Q

Parasite increase vector biting rate / persistence

A

Malaria carrying mosquitoes bite more people, and return to bite if first attempt unsuccessful.

Increase transmission rate.

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14
Q

Parasite modify vector feeding preferences

A

Mosquitoes more likely to bite hosts with transferable form of malaria

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15
Q

Parasite altering host microhabitat perference

A

Parasitic worm infected cockroaches tend to stay in the sun; more likely to be noticed by predator (parasite’s final host)

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16
Q

Enslaver parasites and death grips

A

Parasite controls where host dies.
Fungal infection in ant causes ant to have a death grip on a twig when it dies. Fungal spores burst from ant head. Location could facilitate future growth.

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17
Q

Parasite change web construction of spiders

A

Parasitic wasp infect orb-weaving spiders.
Larvae grow in spiders -> manipulates spider to make cocoon web to protect pupae -> larvae kill spider and pupation stage occurs

18
Q

Can spiders be saved from cocoon web construction?

A

Yes, if the larvae/infection is killed off before cocoon web is constructed. Web making behaviour will MOSTLY return to normal.

19
Q

Parasites cause host suicide

A

Juvenile horsehair worms make crickets (host) to go into water. Will cause death for cricket, but allow horsehair worm to to to ideal environment.

20
Q

Which horsehair worm is parasitic?

A

Juvenile

21
Q

Examples of morphological modifications by the parasite

A
  1. Mimicry in ants

2. Mimicry in snails

22
Q

Parasite-induced mimicry (ants) is caused by which parasite?

A

Nematatodes

23
Q

Parasite-induced mimicry (ants)

A

Nematode cause last abdominal segment in ant to swell up like a berry

  • > bird attracted to berry-ant
  • > ant will go infect rest of its colony
24
Q

Ideal host for nematodes?

A

Bird gut

25
Q

Intermediate host for nematodes?

A

Ants

26
Q

Parasite-induced mimicry (snails) is caused by which parasite?

A

Trematode (L. paradoxicum)

27
Q

Parasite-induced mimicry (snails)

A

Snail eye-stalks resemble caterpillars; snails aren’t able to see as well to avoid predators.

Make snail more likely to be eaten by birds.

28
Q

Ideal host for trematodes?

A

Birds

29
Q

Intermediate host for trematodes?

A

Snails

30
Q

Some snails infected by trematodes live ____

A

longer

31
Q

Are parasites really causing extended phenotype in hosts? (hypothesis)

A
  1. Trait is adaptive for parasite
  2. Trait is adaptive for hosts
  3. Trait is coincidental by-product of infection
32
Q

Analysis of examples: parasite increase vector biting rate / persistence

A

By-product of infection:

mosquitoes that bite more die sooner

33
Q

Analysis of examples: worm cause cockroach to go into sun

A

Host adaptation:

worms want cooler temperature to grow, going into sun will stop development

34
Q

Analysis of examples: death grip in ants

A

Parasite adaptation:
Uninfected ants like to go high in trees. Infected ants stay low to the ground.
Any other elevation lead to bad results for the parasite, so it is the parasite causing the ant to go to specific location.

35
Q

Analysis of examples: cocoon web construction

A

Parasite adaptation:

  • without cocoon nest, pupae tend to die in the rain
  • removing parasite causes spider web-making behaviour to almost return to normal
36
Q

Analysis of examples: host suicide

A

Parasite adaptation:

  • huge cost to host
  • infected hosts more likely to jump in water
  • rescued hosts jump back into water
37
Q

Analysis of examples: zombie snails

A

No answer: complex trait

38
Q

Preferred host by L. paradoxicum

A

wide variety of bird species

39
Q

What would give a answer to the type of adaptation zombie snails are?

A

Quantify if there is an increase in predation of snails that are infected.

40
Q

Why is it important to understand the adaptation behind parasite induced behaviours?

A
  1. Possible treatments
  2. Control vector behaviour to reduce infection
  3. Do proper science

BIO220 (24 decks)

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