Download Inter- and intraspecific parasitism

Inter- and intraspecific parasitism
Dik Heg
The major types of organism-organism
interactions
1. Competition
Interspecific competition (competition between different species)
Intraspecific competition (competition within the same species)
2. Predation
Interspecific predation (predator-prey interactions)
Intraspecific predation (cannibalism, infanticide)
3. Cooperation
Interspecific cooperation (mutualism, symbiosis)
Intraspecific cooperation (kin selection, reciprocal altruism)
4. Parasitism
Interspecific parasitism (host-parasite interactions, e.g.
ectoparasites, endoparasites, viruses, pathogens)
Intraspecific parasitism (within-species brood parasitism, e.g. egg
dumping, sneaking)
Interspecific parasitism: definition
Parasite (pathogen) = organism that obtains its nutrients from one
or a very few host individuals, causing harm* but not
causing host death immediately.
Parasitoid = egg to larval organism that obtains its nutrients from a single host
individual, causing host death in the end (incl. parasitic Hymenoptera
and Diptera insects).
´Host´
Cost
No cost, no benefit
Benefit
Co-species (always benefit)
parasite
commensalist
mutualist or symbiont
Interaction
Parasitism
Commensalism
Mutualism or
Symbiosis
Parasitism
O
Commensalism
Mutualism or Symbiosis
Cost and benefits in terms of fitness: life expectancy (age) * reproductive success/age step
* harm = fitness of host is reduced, though perhaps only in appropriate circumstances (e.g. a
sufficient number of parasites or when the host is in poor body condition)
Interspecific parasitism 1.
Example of the effect of a parasite on survival,
growth and fecundity of a host
Interspecific parasitism 2.
The diversity of interspecific parasites
Microparasites = multiply directly within
their host (usually within the host cells):
bacteria, viruses, protozoa, fungi.
Trypanosoma brucei (sleeping sickness,
Schlafkrankheit)
Parasitic mite
Hydraphantes
tenuabilis
Water bug
Hydrometra
myrae
Macroparasites = grow in their host, but
multiply by producing infective stages
which are released from the host to
infect new hosts (or intermediate hosts).
cestode worms Schistocephalus solidus in
stickleback
Brood parasites = use resources of the host
(e.g. food, shelter), and/or they feed on
larvae or eggs. Often mimicry involved
(e.g. chemical, tactile, morphological).
Special case: slave-making ants.
Interspecific parasitism 3.
Interspecific parasitism 4.
1
in liver
The malaria cycle
Microparasites:
1. Directly transmitted from host to host:
a. immediate transfer: e.g. venereal
diseases, influenza, measles
b. dormant period: e.g. amoebic
dysentry, plant pathogen spores in soil
in blood
Entamoeba histolytica trophozoites (amoebic
dysentry, Amüben-Ruhr)
2.
Indirectly transmitted via some other
species (vector or intermediate
host(s))
Vector: anopheline mosquito
Plasmodium falciparum (malaria)
in mosquito
within red blood cells
Interspecific parasitism 5.
Macroparasites:
platyhelminth worms
(tapeworms, trematodes)
acanthocephalans
(intestinal) nematodes
lice, fleas, ticks, mites,
fungi
1.
Directly transmitted from
host to host
2.
Indirectly transmitted via
some other species (vector
or intermediate host(s))
Plasmodium vivax, after Vickerman & Cox 1967
Interspecific brood parasites
Dactylogyridae worm of fish
Brood parasites = use resources of the host (e.g. food,
shelter), and/or they feed on larvae or eggs.
Many examples in insects, but also some examples
in birds and fish. Most important taxon:
Hymenoptera, e.g. parasitoid wasps
Cleptoparasite = idem,
only uses resources.
Example: Parastizopus armaticeps with
cleptoparasite Eremostibes opacus
(tenebrionid beetles from the Kalahari desert)
Interspecific parasitism 7.
Interspecific parasitism 4.
Example brood parasites: Atemeles pubicollis
Staphylinid beetle
Atemeles pubicollis
enters colony of
Formica rufa
Interspecific parasitism 6.
Beetle larvae
produce glandular
secretion which
induces grooming.
Larva begs to
obtain regurgated
food
Example brood parasites: ant parasites
Limulodid beetle
Paralimulodes
wasmanni on
Neivamyrmex
nigriscens
Mite Circocylliba
sp. on Eciton sp.
Mite
Antennequesoma
sp.on army ant
Interspecific parasitism 9.
Nicoletiid silverfish
Trichatelura manni
on Eciton sp.
Mite Macrocheles
rettenmeyeri on
Eciton dulcius
Histerid beetle
Euxenister caroli
on Eciton burchelli
Interspecific parasitism 10.
2
Example brood parasites: slave-making ants
Slave-maker ant Epimyrma
stumperi enters nest and
strangles, kills....
.... Host queen ant
Leptothorax
tuberum
Population dynamics of directly
transmitted microparasites
Basic reproductive rate:
R0 = Σ lx * mx
lx = proportion of individuals surviving until age x
mx = average number of offspring produced
per individual at age x
Example
Phlox drummondii: R0 = 2.41
This slave-maker ant Formica
subintegra has a large Dufour´s gland
for the production of ´propaganda
substances´ that will scatter the slaveants (also from the genus Formica)
during raids.
For parasites usually Rp is used:
It is contrasted with the Dufour´s
gland of F. subserica, which is an
ordinary ant.
Rp = 1: the transmission threshold
Rp < 1: disease will die out
Rp > 1: disease will spread
Rp = average number of new cases of the disease that arise from each infected host
Interspecific parasitism 11.
Directly transmitted microparasites:
determinants of Rp
Interspecific parasitism 12.
Directly transmitted microparasites:
determinants of Rp
Rp = average number of new cases of the disease that arise from each infected host
Rp = average number of new cases of the disease that arise from each infected host
Rp = β * N * ƒ * L
Rp = β * N * ƒ * L
Where:
β = transmission rate of the disease
= frequency of host contact * probability that host contact leads to infection
(0.0 – 1.0)
Proportion of alive infectious hosts * time alive
Number of new hosts getting infected
N = density of (susceptible) hosts (0.0 - ∞)
ƒ = fraction of hosts that survive long enough to become infectious themselves
(0.0 – 1.0)
L = average period of time over which the infected host remains infectious (>0 - ∞)
Note: in most biotrophic parasites L is the period of the host`s life when it is
infectious, but for necrotrophic parasites and some biotrophs, the parasite may
remain infectious long after the host has died (and decomposed)
Interspecific parasitism 13.
Directly transmitted microparasites:
determinants of Rp
Interspecific parasitism 14.
Vector-transmitted microparasites:
determinants of Rp
Rp = 1: transmission threshold
⇒ Nt =
1
β*ƒ*L
: density threshold
Both the life cycle of the host h and the vector v has to be taken into account:
So if parasites (diseases) are highly infectious (large β), or are unlikely to kill their
host (large ƒ), or give rise to long periods of infectiousness (large L), they will have
high Rp values and can persist in small populations (Nt is small).
Rp = β2 * Nv * ƒv*ƒh * Lv*Lh
Nh
Note: β is squared, because when the vector bites, it both can get infected by the
host itself, or pass the infection to a new host when it is already infected itself.
Hosts acquiring immunity against
parasite versus mutant parasites
arising or influx of new hosts
=> cycles of parasite incidence.
Interspecific parasitism 15.
Interspecific parasitism 16.
3
Vector-transmitted microparasites:
determinants of Rp
For macroparasites it is possible to determine the reproductive success and life
expectancy of a single individual parasite = the sum of offspring produced that
themselves survive to produce offspring.
Rp = average number of new cases of the disease that arise from each infected host
Rp = 1: transmission threshold
⇒ Nv =
Nh
1
β2 * ƒv * ƒh * Lv * Lh
Directly transmitted macroparasites:
determinants of Rp
: the ratio-of-densities threshold
Rp = (λ*ƒa*La) * (β*N*ƒi*Li )
Hence, disease control measures are
usually aimed directly at reducing the
numbers of vectors, and only indirectly at
the parasite. This reduces the likelihood
that the final host (e.g. man) will get
infected, so less direct treatments of the
parasite in the final host are necessary.
Reproductive
contribution of:
Interspecific parasitism 17.
adult
infective stage
λ = rate of egg production per adult parasite
ƒa = proportion of parasites in the host that attain sexual maturity
La = expected life span of adult parasite
β = transmission rate
N = host density
ƒi = proportion of the parasite transmission stage that become infective
Li = expected life span of the infective stage outside the host
Interspecific parasitism 18.
Density-dependence within the host is crucially
important for the reproductive rate of macroparasites
Parasitoids
Parasitoid = egg to larval organism that obtains its nutrients
from a single host individual, causing host death in the
end (incl. parasitic Hymenoptera and Diptera insects).
λ = rate of egg production per
adult parasite
ƒa = proportion of parasites in
the host that attain sexual
maturity
La = expected life span of adult
parasite
extremely numerous group of organisms, since an estimated
25% of the world species are parasitoids (since most
insect species host at least one parasitoid, and some
parasitoids host parasitoids themselves =
superparasitism by same parasite species, or
hyperparasitism by other parasite species)
Interspecific parasitism 19.
Parasitoids hyperparasitism web
Interspecific parasitism 20.
Effects of parasites on behavioural ecology:
case study barn swallow
♀
♂
Interspecific parasitism 21.
♂
♀
Interspecific parasitism 22.
4
Effect of barn swallow parasites on fitness
Barn swallow parasites
Interspecific parasitism 23.
Interspecific parasitism 24.
Effect of barn swallow parasites on fitness
Brood parasitism
Fish: 2-3 species
Birds: ~1% of all species (50% of the cuckoos, two genera of
finches, five cowbirds, and a duck)
Interspecific parasitism 25.
Catfish Synodontis multipunctatus
Brood parasitism by catfish Synodontis
multipunctatus
Number of
broods examined:
Simochromis babaulti &
S. diagramma
Pseudosimochromis
curvifrons
Tropheus moorii
Mouthbrooding
cichlids
% with catfish
Brood parasitism by
catfish from Lake
Tanganyika:
Interspecific parasitism 26.
Host´s eggs and
offspring are
consumed by the
catfish offspring....
Gnathochromis pfefferi
Ctenochromis horei
Interspecific parasitism 27.
Interspecific parasitism 28.
5
Brood parasitism by birds: cuckoo Cuculus canorus
References:
N.B. Davies
and others (1987-2003)
M. & B.Taborsky et al.
Interspecific parasitism 29.
Cuckoo Cuculus canorus
Cuckoo Cuculus canorus: mimicry of host eggs
host
cuckoo model
Robin
(Erithacus rubercula)
Pied wagtail
(Motacilla alba)
(Prunella modularis)
Dunnock
Individual females specialize
on specific host species, e.g.
Reed warbler Acrocephalus
scirpaceus
Meadow pipit Anthus pratensis
Dunnock Prunella modularis
(Acrocephalus scripaceus)
Reed warbler
(Anthus pratensis)
Meadow pipit
Great reed warbler
(Acrocephalus arundinaceus)
Gibbs et al. 2000. Nature
Interspecific parasitism 31.
Cuckoo Cuculus canorus
Cuckoo Cuculus canorus
1985-86
1985-86
Hosts-parasite co-evolution 1.
1997
1997
0
week
10
6
Cuckoo Cuculus canorus
Cuckoo Cuculus canorus
Hosts-parasite co-evolution 2 (Lotem et al. 1995. Animal Behaviour 49: 1185-1209).
Hosts-parasite co-evolution 3.
Host strategy Probability of event
Accept
p parasitized
1-p non-parasitized
The payoff of an accepter will be equal to that of a
rejecter when:
p parasitized
Reject
1-p non-parasitized
Payoff to host
0
X
1-e rejects cuckoo
e rejects own offspring*
1-e no error
e rejects own offspring**
X – 1***
0
X
X-1
X = number of host offspring
* = mistakingly rejects own offspring instead of cuckoo offspring!
** = mistakingly rejects own offspring, despite there is no cuckoo in the nest!!
*** = if the host kills own offspring by removing the parasite (e.g. breaks own eggs), term will be X – 2 ..
Intraspecific parasitism: definition
Conspecific individual using the brood care of other
individuals, without providing brood care
themselves.
Females: egg dumping.
Males: extra-pair fertilizations, sneaker spawning.
(1-p)X = p(1-e)(X+1) + (1-p)(1-e)X + (1-p)e(X+1)
⇒
Rejection error
e = (p-pX)
(2p-pX-1)
Natural parasitism level p is ~3%,
so low rejection error level of ~7-8%
would make payoff accepter = rejecter!
Interspecific parasitism 36.
Intraspecific parasitism:
sperm competition
Females: egg dumping virtually equivalent with
interspecific brood parasitism.
Males: sperm competition plays an important role in the
relative success of extra-pair copulations or sneaker
spawnings.
Sperm competition = the likelihood that sperm of a particular
male will fertilise the ova, depending on the sperm of other
male(s) in the reproductive tract of the female
Intraspecific parasitism 1.
Intraspecific parasitism 1.
7