Lecture 3 Flashcards
What are some characteristics of parasitoids?
- specialized in choice of host
- smaller than host
- only female searches for host
- different parasitoid species can attack different life stages of host
- adults are free-living, mobile and may be predaceous
- eggs or larvae are usually laid in, on or near host
- immature remain on or in host and almost always kill host
What are the life stages of a host that parasitoids may prey on?
egg, larvae, pupae, adult
What are three types of parasitoids (trophic level)?
Primary parasitoid: parasitoids that attack herbivores, such as aphids or caterpillars
hyperparasitoid: parasitoids that attack the larvae and pupae of other parasitoids
pseudo-hyperparasitoid: parasitoid that position higher up in the food web, that parasitize pupae, aphid mummies, predators
What are some modes of parasitism?
ectoparasitoid: larvae live outside on the body of host
endoparasitoid: larvae live inside body of host
koinobiont: sharing life with their host, host continues to feed/grow
idiobiont: living their own life, parasitoid kills or paralyzes host
solitary: only one egg can successfully develop in a host
gregarious: more eggs deposited and successfully developing in one host
What are some herbivore/host immune defenses?
Hemocyte proliferation
Melanotic encapsulation
How do parasitoids overcome host immune responses?
- host immune response with hemocytes aims to encapsulate parasitoid eggs and larvae, parasitoid injects teratocytes (venom) to fight the host immune system
- host immune vigor varies with plant quality, stronger plant resistance reduces host immune response and thus higher survival rate of parasitoid
What is the type of venom usually inserted into the host by the parasitoid?
PDV, macrovirus and ichnovirus
What is the function of PDV?
- PDV and venom regulate host physiology, growth and molting, PDV reduces host immune effectiveness
PDV may even regular behaviour, so that parasitoid larvae have reduced risk of being predated
What is the effect of a solitary vs gregarious larva?
solitary parasitoids have larvae with mandibles to kill competitors, they are often mobile by their tails
gregarious parasitoid larvae lack mandibles and/or tails, gregariousness can evolve only when siblicidal behaviour is reduced/absent
What is a polyembrionic parasitoid?
single embryo develops into many larvae that develop inside the host, some larvae specialize as soldiers to kill unrelated polygerm
What gives solitary parasitoids the advantage during a multiparasitic event?
- solitary parasitoids have larvae with mandibles to kill competitors, they are often mobile by their tails, they may even have glands that release chemical compounds to suppress development of other parasitoid larvae
What are the two oviposition strategies in parasitoids?
pro-ovigenic: all eggs are ready upon emergence of parasitoid from its pupa
syn-ovigenic: parasitoid emerges with limited number of eggs developed and needs protein food source to develop further eggs
What is egg limited and time limited parasitoid species?
egg limited: hosts are abundant and easily found, daily egg production cannot live up with host encounters
time limited: egg loads are large but it is difficult to find hosts, leading to a limitation in time to spend the egg load
What is superparasitism?
two parasitoid individuals of the same species attack the same host individual
What is multiparasitism?
two parasitoid individuals of different species attack the same host individual
What is hyperparasitism?
a parasitoid parasitizes another parasitoid species within the same host
What is heteronomy?
a male parasitoid develops within a female conspecific individual within the host
What is self-superparasitism?
the same female oviposits multiple times in the same host, larvae will compete for the resource
- larvae will kill each other, only one larvae can develop inside the host
How do parasitoids adapt to increased competition by other females?
stay longer on the patch with hosts
self-superparasitize more often
What are the three steps to host location by parasitoids?
localization in host habitat
host location
host acceptance
What is the reliability-detectability paradigm?
reliability: the most reliable cue is one that is directly associated with the host, for example, host body odors
- there is strong selection on hosts not to reveal themselves, thus hosts often do not smell and are conspicuous
detectability: hosts are difficult to detect, due to small size and selection to not reveal themselves
- hosts do have to feed, herbivore hosts induce changes in plant volatiles by damaging the plant during feeding, they provide parasitoids with a cue about the whereabouts of the hosts
How can parasitoids be confused by herbivore induced plant volatiles (HIPVs)?
when other herbivores are feeding alongside hosts and odor profiles of neighboring or the same plant that are damaged by non hosts confuse parasitoids
What do parasitoids do after arrival on the herbivore host plant?
look for hosts and use patch exploitation decisions that further optimize foraging decisions
What is fixed searching time?
some parasitoids use a fixed searching time rule, independent of encounters
