Lecture 6 Flashcards
parasitoid
parasitic while immature but free-living as an adult
What distinguishes parasitoids from parasites?
Ultimately kills the host to complete its own life cycle (doesn’t occur in parasites)
____ % of all described insect species are parasitoids
10%
what portion of Hymenoptera species are parasitoids?
3/4
what portion of Diptera & Coleoptera species are parasitoids?
1/4
how many insect orders include parasitoids? & where how many have most of the diversity?
7
3
what order includes the bulk of parasitoid diversity? & what are 3 ex?
Hymenoptera (most families of wasps are parasitoids)
ex: Braconid wasps
ex: ichneumonid wasps
ex: chalcid wasps
braconid wasps attack what type of insects?
insects with holometabolous development
what is likely the most diverse animal & insect family?
ichneumonid wasps of Hymenoptera
what do ichneumonid wasps eat?
Attack broad range of insects
spiders
centipedes (not insects)
chalcid wasps
super family
small
metallic
what order are staphylinid beetles in?
coleoptera
what is the largest animal family?
staphylinid beetles
what are the 7 orders with parasitoids?
3 main: Hymenoptera, Diptera & Coleoptera
4 others: Lepidoptera, Trichoptera, Neuroptera, Strepsitera
what is the 2nd largest family of flies?
tachinid flies
who do tachinid flies attack?
generalists
attack caterpillar & sawflies
ectoparasitoid
larval stage feeds from outside of host
endoparasitoid
larval stage feeds from inside host
egg is implanted on the inside of the body & feeds on the inside of the host
how do you determine the number of offspring produced per host?
depends on the size of the paraistoid compared to its host
solitary parasitoid
one larvae develops on/in host
gregarious parasitoid
multiple larvae develop in/on a single host
results form multiple eggs
polyembryonic parasitoid
produce multiple offspring from a single egg
eggs undergo fission
idiobiont
host growth stops at time of parasitism (as soon as host is parasitized, the host development stops)
mother injects venom immobilizing the host
primarily of ectoparasitoids or endoparasitoids of immobile phases
koinobiont
host continues to feed, act normally & develop normally as parasitoids are developing within it
injections alter immune system
primarily endoparasitoids
parasitoid receives constant nutrition & protection
parasitoids are only assoc with host during what stages?
egg
larval
Pupa
primary parasitoid
attacks non-parasitoid host
hyperparasitoid
attacks another parasitoid
What forms of defense can help potential hosts to escape or otherwise reduce the impact of parasitoid activities? (3)
behavioural defenses
chemical defenses
immune responses
behavioural responses (8)
o Wriggling o Aggregation o Spitting o Kicking o Running o Dropping o Flying o Movement away from conspecifics
chemical defense
ex: alarm pheromone release - invokes response in all other aphids in a colony
when do immune responses occur?
if eggs are deposited into the hemolymph
describe the process of when an immune response occurs?
hemocytes adhere to & form a capsule around the egg (of the parasitoid)
the capsule can melanize & suffocate the egg preventing it from hatching
How do parasitoids overcome host defenses?
behavioural modification
specialized morphology
venom
polydna viruses
what are some exs of behavioural modifications in hosts of parasitoids?
ex: parasitized caterpillars may actually increase consumption, thereby producing larger & more fecund parasitoids
ex: parasitized aphids move away from patches to the other side of leaves
how do parasitoids have specialized morphology to overcome host defenses?
Laying eggs into host – highly modified ovipositors
Ex: parasitoid wasps have bits of metals to insert the eggs
Ovipositors can taste to ensure that they are injecting into the correct host
how do parasitoids use their venom to overcome host defenses? (4)
paralytic activity
Disrupt hemocyte adhesion – increasing likelihood that the egg will hatch
Prevent host molting
Ectoparasitoid koinobionts
When a host molts it will shed the ectoparasitoid
May disrupt endocrine system & disrupt hormones important for molting
Severe metabolic alterations
Ex: make host more nutritious – make lipids available
polydna virus
Integrated into wasp genomes
Replicates in wasp ovaries & integrates into host genome
Cause immune response breakdown upon injection into host – prevents host from responding to egg
Disrupts encapsulation
Prevents nutritive uptake
Breaks down immune response & makes host more nutritious at the same time
