Inter- and intraspecific parasitism interactionsbehav.zoology.unibe.ch/sysuif/uploads/files/Parasitism.pdf · 1 Inter- and intraspecific parasitism Dik Heg The major types of organism-organism

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Inter- and intraspecific parasitismDik 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: definitionParasite (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´ Co-species (always benefit) InteractionCost parasite ParasitismNo cost, no benefit commensalist CommensalismBenefit mutualist or symbiont 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.

Parasitism

Commensalism

Mutualism or Symbiosis

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Example of the effect of a parasite on survival, growth and fecundity of a host

Water bug Hydrometra myrae

Parasitic mite Hydraphantes tenuabilis

The diversity of interspecific parasites

Microparasites = multiply directly within their host (usually within the host cells): bacteria, viruses, protozoa, fungi.

Macroparasites = grow in their host, but multiply by producing infective stages which are released from the host to infect new hosts (or intermediate hosts).

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.

Trypanosoma brucei (sleeping sickness, Schlafkrankheit)

cestode worms Schistocephalus solidus in stickleback


Microparasites:1. Directly transmitted from host to host:

a. immediate transfer: e.g. venereal diseases, influenza, measlesb. dormant period: e.g. amoebic dysentry, plant pathogen spores in soil

2. Indirectly transmitted via some other species (vector or intermediate host(s))

Entamoeba histolytica trophozoites (amoebic dysentry, Amüben-Ruhr)

Plasmodium falciparum (malaria)

within red blood cells

Vector: anopheline mosquito


The malaria cycle in liver in blood

Plasmodium vivax, after Vickerman & Cox 1967

in mosquitoInterspecific parasitism 6.

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Macroparasites:platyhelminth worms (tapeworms, trematodes)acanthocephalans(intestinal) nematodeslice, fleas, ticks, mites, fungi

1. Directly transmitted from host to host

2. Indirectly transmitted via some other species (vector or intermediate host(s))

Dactylogyridae worm of fish


Interspecific brood parasites

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 withcleptoparasite Eremostibes opacus(tenebrionid beetles from the Kalahari desert)


Example brood parasites: Atemeles pubicollis

Staphylinid beetle Atemeles pubicollisenters colony of Formica rufa

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.

Nicoletiid silverfish Trichatelura mannion Eciton sp.

Mite Macrocheles rettenmeyeri on Eciton dulcius

Mite Antennequesoma sp.on army ant

Histerid beetle Euxenister carolion Eciton burchelli


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Example brood parasites: slave-making antsSlave-maker ant Epimyrma stumperi enters nest and strangles, kills....

This slave-maker ant Formica subintegra has a large Dufour´s gland for the production of ´propaganda substances´ that will scatter the slave-ants (also from the genus Formica) during raids.

It is contrasted with the Dufour´s gland of F. subserica, which is an ordinary ant.

.... 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 xmx = average number of offspring produced

per individual at age x

For parasites usually Rp is used:

Rp = average number of new cases of the disease that arise from each infected host

Rp = 1: the transmission thresholdRp < 1: disease will die outRp > 1: disease will spread

ExamplePhlox drummondii: R0 = 2.41

Directly transmitted microparasites:determinants of Rp



Rp = β * N * ƒ * LWhere:

β = transmission rate of the disease = frequency of host contact * probability that host contact leads to infection

(0.0 – 1.0)

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 - ∞)



Rp = β * N * ƒ * L

Number of new hosts getting infected

Proportion of alive infectious hosts * time alive

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)


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Rp = 1: transmission threshold

⇒ Nt = 1 : density thresholdβ * ƒ * L

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).

Hosts acquiring immunity against parasite versus mutant parasites arising or influx of new hosts=> cycles of parasite incidence.

Vector-transmitted microparasites:determinants of Rp


Both the life cycle of the host h and the vector v has to be taken into account:

Rp = β2 * Nv * ƒv*ƒh * Lv*LhNh

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.

Vector-transmitted microparasites:determinants of Rp


Rp = 1: transmission threshold

⇒ Nv = 1 : the ratio-of-densities thresholdNh β2 * ƒv * ƒh * Lv * Lh

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.

Directly transmitted macroparasites: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 = (λ*ƒa*La) * (β*N*ƒi*Li )

Reproductive contribution of:

adult infective stage

λ = rate of egg production per adult parasiteƒa = proportion of parasites in the host that attain sexual maturityLa = expected life span of adult parasiteβ = transmission rateN = host densityƒi = proportion of the parasite transmission stage that become infectiveLi = expected life span of the infective stage outside the host

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Density-dependence within the host is crucially important for the reproductive rate of macroparasites


λ = rate of egg production per adult parasiteƒa = proportion of parasites in the host that attain sexual maturityLa = expected life span of adult parasite

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).

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)


Parasitoids hyperparasitism web


Effects of parasites on behavioural ecology: case study barn swallow

♂♂

♀ ♀


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Barn swallow parasites


Effect of barn swallow parasites on fitness


Effect of barn swallow parasites on fitness


Brood parasitism

Fish: 2-3 speciesBirds: ~1% of all species (50% of the cuckoos, two genera of

finches, five cowbirds, and a duck)


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Brood parasitism by catfish from Lake

Tanganyika:

Catfish Synodontis multipunctatus

Simochromis babaulti & S. diagramma

Tropheus moorii

Ctenochromis horei

Gnathochromis pfefferi

Pseudosimochromis curvifrons

Mouthbrooding cichlids


Brood parasitism by catfish Synodontis multipunctatus

Number of broods examined:

% w

ith c

atfis

h

Host´s eggs and offspring are consumed by the catfish offspring....


Brood parasitism by birds: cuckoo Cuculus canorus


References:N.B. Davies and others (1987-2003)M. & B.Taborsky et al.

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Cuckoo Cuculus canorus: mimicry of host eggshost cuckoo model

Robin

Pied wagtail

Dunnock

Reed warbler

Meadow pipit

Great reed warbler

(Erithacus rubercula)

(Motacilla alba)

(Prunella modularis)

(Acrocephalus scripaceus)

(Anthus pratensis)

(Acrocephalus arundinaceus)


Cuckoo Cuculus canorus

Individual females specialize on specific host species, e.g.

Reed warbler Acrocephalus scirpaceus

Meadow pipit Anthus pratensisDunnock Prunella modularis

Gibbs et al. 2000. Nature


Hosts-parasite co-evolution 1.


1985-86

1997

1985-86

1997

week0 10

10


Hosts-parasite co-evolution 2 (Lotem et al. 1995. Animal Behaviour 49: 1185-1209).

Host strategy Probability of event Payoff to hostAccept p parasitized 0

1-p non-parasitized X

p parasitized 1-e rejects cuckoo X – 1***

Reject e rejects own offspring* 01-p non-parasitized 1-e no error X

e rejects own offspring** X - 1X = 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 ..


Hosts-parasite co-evolution 3.

The payoff of an accepter will be equal to that of a rejecter when:

(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!


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.

Intraspecific parasitism 1.

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.

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Inter- and intraspecific parasitism interactionsbehav.zoology.unibe.ch/sysuif/uploads/files/Parasitism.pdf · 1 Inter- and intraspecific parasitism Dik Heg The major types of organism-organism