VL 9

Question 1

Predator

Answer 1

Animal that kills and consumes other animals (prey) and requires multiple prey items to reach maturity

Question 2

Parasite

Answer 2

An organism living on or in another living organism, obtaining its nutrition from that organism and causing some kind of measurable damage to the host. Will spend most of its life on a single host, but rarely kills it. Close long term interaction

Question 3

Insect herbivores as parasites

Answer 3

Many insect herbivores fit this broad definition

Insect herbivores can be called plant parasites, seed predators or seed parasitoids

Question 4

Parasitoids

Answer 4

free living insects as adults, but lay their eggs within or on another host. The immature parasitoid will develop parasitically on the host and eventually kill it

Question 5

Are blood feeding insects parasites?

Answer 5

Most disease vectoring insects are not parasites by definition

However, some insects, such as bed bugs, are considered parasitic due to their obligate, close association with hosts

Question 6

How can parasites affect the host?

Answer 6

can moderate trophic dynamics and competition - ‘ecosystem engineers’

can affect behaviour of host or decrease its reproduction ot development in order to benefit themselves and their own growth / survival / reproduction - divert resources

Question 7

Ectoparasite

Answer 7

Live on the body surface

Feed on blood or epidermis

Usually have specialized structures to cling to the body of the host

Eg. lice, bat bugs, bed bugs, varroa mites

Question 8

Endoparasites

Answer 8

Undergo most of life cycle inside the host, except for moving to new hosts

Feed on host internal tissues or live inside host cavities or spaces

Need to combat immune system or avoid too much damage to host

eg. Strepsiptera, Bot flies

Question 9

Endoparasites - Strepsiptera

Answer 9

endoparasites of ants, bees, wasps, leafhoppers, cockroaches

Most larval stages and the adult females are parasitic, males are free living

Question 10

Endoparasites - Bot flies

Answer 10

The larvae are endoparasites of many different mammal species
- myiasis: the parasitic infestation of the body of a mammal by a fly larvae

Feed on tissue under the host’s skin or within the host’s gut

Often have complex behaviour involving using other insects to vector their eggs

Question 11

How many insects are parasitoids?

Answer 11

10% of all known insect species are parasitoids

Most parasitoids (75%) are wasps (Hymenoptera) belonging to the superfamilies Chalcidoidea or Ichneumonoidea. The other important parasitoid group is the Family Tachinidae in the Diptera

Specialized, making them useful for biocontrol programs. They inject venom and eggs directly into hosts

Question 12

Parasitoid classification

Answer 12

Where they lay eggs - endoparasitoids / ectoparaitoids

How they attack their host - Idiobionts (immobile host stages or cause permanent immobilization) / Koinobionts (mobile hosts)

Number of offspring per host - solitary / gregarious

Question 13

Idiobiont ectoparasitoids

Answer 13

paralyze host with venom, offspring develops outside host

do not have to overcome immune response - feed externally on paralyzed organism, but vulnerable to predators

Question 14

Idiobiont endoparasitoids

Answer 14

attack sessile life stages (eggs, pupae), offspring develop in host

have to overwhelm host immune system
some inject a venom or virus alongside the eggs to aid this

Question 15

Koinobiont ectoparasitoids

Answer 15

offspring feeds on growing host exterior

Have to avoid being brushed off by the host’s molting, as well as desiccation and being exposed to hyperparasitoids

Question 16

Koinobiont endoparasitoids

Answer 16

very diverse; offspring develop inside the host and cause a variety of physiological changes

Tightl linked to the biology of their hosts. Tend to be very specialized. Must evade / overwhelm continuously functioning immune system

Question 17

Example of both endo or ecto parasite

Answer 17

The jewel wasp, Ampulex compressa, immobilises its cockroach host and lays an egg on the abdomen

The larvae feeds for 4 days on the outside of the cockroach, then chews its way into the abdomen and feeds internally

It carefully consumes the organs in an order which keeps the host alive for as long as possible

Question 18

What are adaptations of parasites and prarsitoids?

Answer 18

Small body size
Specificity

Question 19

Adaptation - specifity

Answer 19

Parasitoid: 90% of all parasitoid wasps attack only one or two host species

Bird lice: 87% recorded only a single host species

Parasites / parasitoids tend to have very intimate interactions with their hosts, specializing to bypass host defenses / behavior or fit within host body regions

Question 20

Specificity - co-speciation

Answer 20

Parasites speciate alongside their hosts - dependent on its host and must adapt with it

This is most expected when parasites cannot move long distances or are transmitted from parents to offspring (vertical transmission)

Lice are prime examples of this type of parasite

Question 21

Host immune response to parasitoids

Answer 21

Foreign objects are attacked by immune system

Parasitoid egg / larvae ‘encapsulated’ by caterpillar hemocytes, then broken down

Question 22

Parasitoid adaptation to host immune response

Answer 22

Venom secreted with eggs kill host immune cells

PolyDNA-virus replicates in parasitic wasp ovaries - >Virus particles secreted with wasp eggs

Question 23

Immune response - parasitoids: PolyDNA virus

Answer 23

PolyDNA virus enters host tissue with egs and triggers release of proteins that disrupt encapsulation reaction

Host immune response delayed

Wasp larvae can develop inside host without interference

Question 24

Host immune response - malaria

Answer 24

If there is damage consistent with parasite presence in a mosquito gut cell -> apoptosis and cell death

Encapsulation of parasites with melanin to help sequester and kill them (melanization)

Question 25

Parasite adaptation to host response (Malaria)

Answer 25

Can switch to neighbouring, naïve gut cells to avoid cell death

Co-evolved Plasmodium strains evade recognition by incorporationg host proteins

Question 26

Do parasites influence their hist’s behaviour?

Answer 26

Parasites may alter the behaviour of the host to enhance their own transmission

example:
Crickets with parasitic horsehair worms suicidally leap into water, where the worm’s next life cycle stage occurs, due to neurotransmitters produced by the parasite

Ophiocordyceps fungus affects the nervous system of ants, causing them to climb before they die so that the spores can spread further

Question 27

Does malaria manipulate mosquitoes?

Answer 27

Plasmodium parasites have separate life cycles in mosquitoes and humans

In order to be transmitted, a mosquito must bite an infected host, survive until the parasite migrates to the salivary glands, and then bite another potential host

These are the three stages at which transmission potential could be influenced by the parasite

Question 28

How does malaria manipulate mosquitoes?

Answer 28

Mice which had the transmissible stage of Plasmodium parasite were more attractive to mosquitoes

These mice emitted different amounts of volatile compounds than uninfected mice. The same happens in humans

Question 29

How does malaria manipulate the vector?

Answer 29

Mosquitoes carrying the transmissible stage of malaria are more attracted to human odour than uninfected mosquitoes and will bite more often

Mosquitoes carrying the non-transmissible stage may be less attracted to humans, reducing the risk of mortality and therefore more likely to survive until able to transmit

Question 30

What types of plant viruses are transmitted by aphids?

Answer 30

non-persistent (mechanical)
persistent (propagative and circulative)

Each plant virus species is only on eof these types

each type has different transmission dynamics which take advantage of insect feeding behaviour / ecology

Question 31

How are plant viruses aquired? (Non persistent)

Answer 31

Acquired during short-term probing phase

Virions located in epidermal cells of plant become “stuck” to the inside of the aphid’s mouthparts - mechanical transmission$$WHen the aphid next probes, the virion detach and enter the new cell the aphid is probing

Therefore requires that the aphid does not stay and feed

Question 32

How are viruses aquired? (Persistent)

Answer 32

Acquired during long-term feeding stage

Virions in the phloem cells are taken up when the aphid begins consuming phloem sap

Replicate in aphid gut and also infect the aphid

Requires that aphids reach the “ingestion” phase of their feeding behavior on both first and second host

Question 33

Why don’t all parasites / pathogens manipulate their hosts?

Answer 33

Selection only when high transmission pressure

Scarcity of hosts / vectors

Length of transmission period