Week 10

Question 1

What are the 3 strategies parasites use for prolonging an infection?

Answer 1

Fecundity reduction
Gigantism
Escaping behaviour

Question 2

Why do parasites castrate hosts?

Answer 2

Huge amount of energy goes into reproduction, these get redirected and used by parasites

Question 3

How can hosts impact fecundity?

Answer 3

They either fully and partially castrate hosts

Question 4

How did Sacculina (barnacles) impact fecundity of host crabs?

Answer 4

They fully infect crab nerve system. Feminise male crabs and both male and female form brood pouch. They behave like female crabs would do with their own brood and wave their claws in front dispersing parasite eggs

Question 5

How do hosts responsed evolutionairy to castration of hosts?

Answer 5

They mature earlier to get eggs out quickier, but at a cost of overall eggs if they waited and didnt get infected

Question 6

How does parasite infection cause gigantism?

Answer 6

Resources are strategically reallocated to invest into host body growth, maintenance and survival

Question 7

What is a common way to reallocate resources?

Answer 7

Castration

Question 8

Which type of parasites benefit from gigantism?

Answer 8

Slow growing parasites, as gigantism allows for longer infective periods

Question 9

What is the potential benefit of gigantism of hosts for parasites?

Answer 9

Potential ensuring storage for resources from the host for the parasite to use later

Question 10

How does the parasite Pasteuria ramosa (bacteria) impact Daphnia magna reproduction and size?

Answer 10

Infected individuals are bigger than not
Infected individuals have younger age of reproduction
Infected individuals in high food have die youngest followed by infected in low food then uninfected
High food areas have more parasites

Question 11

What are the 4 main methods for increasing parasite transmission?

Answer 11

Changing host behaviour and morphology
Transmission routs
Social behaviour
Neuronal change

Question 12

How do Dracunculus (nematode) change host behaviour?

Answer 12

Females cause a painful blister that feels like burning so the definitve host, mammal including humans, so they put the blister in water which is what the parasite wants allowing eggs to be released

Question 13

What are the symptoms of Cordyceps fungus when they infect ants?

Answer 13

Ants fall down more
Movement is less directional
Death grip accompanied by muscle atrophy the mouth

Question 14

What are the steps for Cordyceps fungus infection and transmission?

Answer 14

1- Ants pick up fungus spore from the forest floor
2- Fungal cell population grows beside the ants brain and secretes an array of metabolites which takes over CNS
3- Secreted metabolites manipulate the ants behaviour causing convulsions and climbing the leaf at optimal height
4- Fungal cell population grows within the ant’s mandibular muscles, altering organelle numbers and amino acid balance
5- Mandibilar muscle atrophy results in the lock-jaw behaviour
6- Stem sprouts out of dead ant releasing spores

Question 15

How do toxoplasma impact rat behaviour?

Answer 15

Attracted to cat odour
Prefer easy rewards
More likely to take risks

Question 16

What are the 2 comman ways of changing host morphology?

Answer 16

Colouration and odour

Question 17

How does the digenea (trematode) Leucochloridium paradoxum imoact land snails?

Answer 17

Change in colouration (mimic caterpillars)
Increased movement up trees

Question 18

How do cestode parasites impact the ant (Leptothorax nylanderi)?

Answer 18

Change in colour (yellowy) and sluggish behaviour
Hydrocarbon alteration -effects cues to nest mates

Question 19

How does Wolbachia impact host populations?

Answer 19

Kill or feminise males in the embryonic stages or induce thelytokous parthenogenesis where virgin females produce daughters
Altering sex rations favouring females

Question 20

Why do Wolbachia feminise or kill male embryos/

Answer 20

They have higher veritical transmission down the female line
Transmitted by females through eggs to the progeny

Question 21

How is the Wolbachia induced sex ratio maintained?

Answer 21

Infected females have a reproductive advantage over uninfected females.
As infected males are incompatible with uninfected females

Question 22

How does Dinocampus coccinellae (parasitoid wasp) have draw backs when infecting lady birds?

Answer 22

When wasps cocoon after emerging form ladybirds, the alive lady birds shelters overthem, this increases egg surivival but decreases fecundity

Question 23

How do flukes have a cost to manipulating ants?

Answer 23

One fluke goes to brain while rest goes to hemolymph. The brain fluke makes ant go to top of grass blade at night to be eaten but returns to normal during the day. When ant is eaten brain fluke doesnt carry on its life cycle?

Question 24

Why does the brain fluke still benefit even though it doesnt reporduce?

Answer 24

The other flukes are most often siblings so brain fluke’s DNA still passes on

Question 25

What are the 4 things ecology is primarily interested in?

Answer 25

Abundance of species
Distrubution of species
Abiotic and Biotic factors
Relationships between species

Question 26

What are the 2 mains reasons why parasites fail to be apparent in a bio-region?

Answer 26

‘Missed the boat’ hypothesis = Parasites were absent in the hosts that intially invaded
‘Drowned on arrival’ hypothesis = Were present in invading hosts but either host or parasites failed to established

Question 27

How can parasites cause ‘drowned on arrival’ for hosts?

Answer 27

Migrating/invasion may be taxing for individulas of the host species, if parasite infections reduce survival, longevity or fitness the infected host individuals may not make it into the founding population

Question 28

What is the founder effect and bottle neck?

Answer 28

Generally only a small number of host individuals start a founding population (parasites will need to be present in that small population and also survive the bottle neck themselves)

Question 29

What can ‘drown’ a parasite even if they survive the inital bottle neck?

Answer 29

They may still need to find new suitable intermediates or vectors

Question 30

What happens to parasite number in an invading species?

Answer 30

There is a loss of parasites in an invading host species

Question 31

What form of transmission is predicted to allow for greater survival of invasion/migration of host?

Answer 31

It is predicted that vertical transmission will do better than horizontal transmission

Question 32

What is parasite spill over?

Answer 32

When invading hosts carry parasites that then spill over into the native resident community

Question 33

How frequent is parasite spill over?

Answer 33

This is quite rare but can be devastating to the native community- it can trigger extinctions

Question 34

What happen with parasite spill over in hawaii?

Answer 34

Avian malaria was introduced to Hawaii and thought to have wiped out half of native species

Question 35

What is parasite spill over?

Answer 35

Conversely, native residents parasites can also spill over into the invading host species

Question 36

What is the impact of parasite spill over on new species?

Answer 36

The influx of new hosts this can facilitate spread in the native community as well as leading to the extinction of the invading host population

Question 37

What happened with the introduction of avian malaria to New Zealand?

Answer 37

Exotic avian in NZ comprised over 30 species from 14 families (mostly introduced by Victorian colonisers)
Several strains of avain malaria have been found in NZ - these are phylogenetically distant so unlikely to have come over in a single endemic radiation event