Week 10 Flashcards
What are the 3 strategies parasites use for prolonging an infection?
Fecundity reduction
Gigantism
Escaping behaviour
Why do parasites castrate hosts?
Huge amount of energy goes into reproduction, these get redirected and used by parasites
How can hosts impact fecundity?
They either fully and partially castrate hosts
How did Sacculina (barnacles) impact fecundity of host crabs?
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
How do hosts responsed evolutionairy to castration of hosts?
They mature earlier to get eggs out quickier, but at a cost of overall eggs if they waited and didnt get infected
How does parasite infection cause gigantism?
Resources are strategically reallocated to invest into host body growth, maintenance and survival
What is a common way to reallocate resources?
Castration
Which type of parasites benefit from gigantism?
Slow growing parasites, as gigantism allows for longer infective periods
What is the potential benefit of gigantism of hosts for parasites?
Potential ensuring storage for resources from the host for the parasite to use later
How does the parasite Pasteuria ramosa (bacteria) impact Daphnia magna reproduction and size?
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
What are the 4 main methods for increasing parasite transmission?
Changing host behaviour and morphology
Transmission routs
Social behaviour
Neuronal change
How do Dracunculus (nematode) change host behaviour?
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
What are the symptoms of Cordyceps fungus when they infect ants?
Ants fall down more
Movement is less directional
Death grip accompanied by muscle atrophy the mouth
What are the steps for Cordyceps fungus infection and transmission?
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
How do toxoplasma impact rat behaviour?
Attracted to cat odour
Prefer easy rewards
More likely to take risks
What are the 2 comman ways of changing host morphology?
Colouration and odour
How does the digenea (trematode) Leucochloridium paradoxum imoact land snails?
Change in colouration (mimic caterpillars)
Increased movement up trees
How do cestode parasites impact the ant (Leptothorax nylanderi)?
Change in colour (yellowy) and sluggish behaviour
Hydrocarbon alteration -effects cues to nest mates
How does Wolbachia impact host populations?
Kill or feminise males in the embryonic stages or induce thelytokous parthenogenesis where virgin females produce daughters
Altering sex rations favouring females
Why do Wolbachia feminise or kill male embryos/
They have higher veritical transmission down the female line
Transmitted by females through eggs to the progeny
How is the Wolbachia induced sex ratio maintained?
Infected females have a reproductive advantage over uninfected females.
As infected males are incompatible with uninfected females
How does Dinocampus coccinellae (parasitoid wasp) have draw backs when infecting lady birds?
When wasps cocoon after emerging form ladybirds, the alive lady birds shelters overthem, this increases egg surivival but decreases fecundity
How do flukes have a cost to manipulating ants?
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?
Why does the brain fluke still benefit even though it doesnt reporduce?
The other flukes are most often siblings so brain fluke’s DNA still passes on
What are the 4 things ecology is primarily interested in?
Abundance of species
Distrubution of species
Abiotic and Biotic factors
Relationships between species
What are the 2 mains reasons why parasites fail to be apparent in a bio-region?
‘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
How can parasites cause ‘drowned on arrival’ for hosts?
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
What is the founder effect and bottle neck?
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)
What can ‘drown’ a parasite even if they survive the inital bottle neck?
They may still need to find new suitable intermediates or vectors
What happens to parasite number in an invading species?
There is a loss of parasites in an invading host species
What form of transmission is predicted to allow for greater survival of invasion/migration of host?
It is predicted that vertical transmission will do better than horizontal transmission
What is parasite spill over?
When invading hosts carry parasites that then spill over into the native resident community
How frequent is parasite spill over?
This is quite rare but can be devastating to the native community- it can trigger extinctions
What happen with parasite spill over in hawaii?
Avian malaria was introduced to Hawaii and thought to have wiped out half of native species
What is parasite spill over?
Conversely, native residents parasites can also spill over into the invading host species
What is the impact of parasite spill over on new species?
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
What happened with the introduction of avian malaria to New Zealand?
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
