Lecture 11 - Invertebrate life histories II

Question 1

What is synchronised emergence?

Answer 1

When cicadas all emerge together in huge numbers

Question 2

What is the purpose synchronised emergence?

Answer 2

predator satiation: having so many individuals that predators can’t eat them all.

Question 3

What is the purpose of prime number life cycles?

Answer 3

predators unable to ‘track’ when the cicadas will emerge

Question 4

How long are prime number life cycles?

Answer 4

13 years

17 years

Question 5

What is a cicada Brood?

Answer 5

all cicadas that emerge in a

particular year

Question 6

What causes temporal reproductive isolation in cicadas?

Answer 6

broods emerge in different years

Question 7

Do members of the same species always have the same brood length?

Answer 7

no some species have both 13 & 17 year forms
17 year form: favoured in cold conditions
13 year form: favoured in warm conditions

Question 8

What is a Parasite?

Answer 8

An organism that lives in or on a second organism (host), gaining benefits at the expense of the host

Question 9

What are the key characteristics of a parasite?

Answer 9

• dependent on host for all or some of their nourishment
• smaller than the host
• temporary or permanent
• highly specialised mode of life
• highly diverse
• life history modifications

Question 10

What are the different types of Parasite?

Answer 10

ectoparasite
endoparasite
parasitoid

Question 11

What is a ectoparasite?

Answer 11

live on the outer surface of the host
e.g. skin, hair
attachment structures (hooks, suckers, teeth)

Question 12

What is a endoparasite?

Answer 12

live inside the host’s body

e.g. intestines, lungs, liver, muscles, internal organs, blood

Question 13

What is a parasitoid?

Answer 13

insects whose larvae develop by feeding upon the bodies of other arthropods (usually insects), resulting in the death of the host
Hymenoptera (wasps), Diptera (flies)
intermediate between parasites and predators

Question 14

What are hyperparasitoids?

Answer 14

parasitoids of parasitoids

Question 15

What groups have ectoparasites?

Answer 15

Porifera 
Cnidaria (hydroids, sea anemones) 
Platyhelminthes
Mollusca (larvae, adults; e.g. bivalves) 
Annelida (leeches, polychaetes) 
Arachnids (mites, ticks) 
Crustacea
Insects
Rotifera

Question 16

What groups have endoparasites?

Answer 16

Platyhelminthes
Orthonectida X
Dicyemida X
Mollusca
Insects
Nematodes 
Nematomorpha
Ancanthocephala

Question 17

What groups have Parasitoids?

Answer 17

Hympenoptera, Diptera

Question 18

How do ectoparasites locate hosts?

Answer 18

active search

waiting within specific microhabitats

Question 19

How do ectoparasites feed?

Answer 19

via mouth

Question 20

What environments do endoparasites live in?

Answer 20

respiratory passages, gut, tissues, blood

Question 21

What are the advantages of living in a host?

Answer 21

stable
resources provide for
protected from physical removal

Question 22

What are the disadvantages of being a endoparasite?

Answer 22

exposed to host defenses (chemical, immune system)
gut: acidic, anoxic, digestive enzymes
difficulty in entering and exiting the host

Question 23

What strategies are employed by endoparasites to enter hosts?

Answer 23

active search: ciliated free-living larvae (marine/aquatic)
burrow through skin, mouth (food, prey items), body openings
difficulty surviving within terrestrial environment

Question 24

What strategies are employed by endoparasites for existing hosts?

Answer 24

intermediate host (predation)
mouth
excreted
through skin
vectors (e.g. mosquitos, ticks, mites)

Question 25

What measures do hosts employ to defend against parasites?

Answer 25

attempt to evict/kill the parasite
non-specific (humoral): untargeted chemical
specific (immune system): targeted with ‘memory’
Major Histocompatibility Complex (MHC): vertebrates

Question 26

What countermeasures can parasites employ do defend against immune systems?

Answer 26

physical protection
detoxification
continually change antigens
active suppression of immune system
hormones that act on host receptors
immunologically privileged sites (host defenses reduced)

Question 27

What are the difficulties of host transmission?

Answer 27

hosts have finite lifetime: need to move between hosts

mortality of propagules often high

Question 28

What transmission strategies do hosts employ?

Answer 28

complex life cycles (multiple hosts, intermediate hosts, vectors)
synchronise reproduction
manipulate host appearance/behaviour

Question 29

What are the differences between parasitic and free living Nematodes?

Answer 29

• larger body size in parasitic species
• nematode body size related to host body size
• increased fecundity in parasitic species