Tasmanian Devils Flashcards

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1
Q

Devil Facial Tumour Disease

A
  • Emerged in NE TAS in 1996
  • Currently recorded over 59% of TAS
  • Local declines of up to 90%
  • Restricted to devils
  • Devils likely to be extinct in 5-25 years
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2
Q

Severity of the disease

A
  • Tumours grow rapidly without any local immune response

- Fatal within 6 months of first lesions (due to starvation, secondary infections or metastases

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3
Q

DFTD Histology

A
  • All tumours appear microscopically similar
  • Originate in the dermis or oral submucosal CT
  • Frequently metastasise (65% of cases)
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4
Q

DFTD Pathology

A
  • Clonally derived from neural crest lineage cells at least 15 years ago, probably Schwann cells
  • Cell implantation during biting
  • DFTD cells from diff devils are identical at microsatellite markers and MHC genes
  • 4 closely related by karyotypically distinct strains
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5
Q

DFTD Transmission

A
  • “Infectious” - direct contact required (cell implantation during biting)
  • Incubation period not known
  • Nearly all between 2 & 3 yr - fighting at sexual maturity
  • No sex predilection
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6
Q

Popular hypothesis for why the tumour is not attacked by immune system

A

No rejection due to lack of genetic diversity in devils

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7
Q

Low genetic diversity in Tassie Devils

A
  • Low diversity across genome, including Major Histocompatability Complex
  • MHC a key region involved in immune response - self/non-self recognition
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8
Q

Low genetic diversity in Cheetahs

A
  • Genetic bottleneck –> very low genetic diversity
  • Skin grafts between unrelated cheetahs are not rejected
  • Very vulnerable to infectious pathogens
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9
Q

Canine Transmissible Venereal Tumour (CTVT)

A
  • Thought to have developed in inbred wolves lacking MHC diversity
  • Spread onto mucous membranes by direct contact or implanted subcutaneously in bite wounds
  • Not prevalent in wolf populations –> does not seem to be a relationship between low genetic diversity and prevalence of CTVT
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10
Q

Evidence FOR the low genetic diversity hypothesis

A
  • Very low genetic diversity in devils, including MHC
  • Cheetahs do not reject skin grafts of unrelated individuals
  • DFTD tumours not rejected
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11
Q

Evidence AGAINST the low genetic diversity hypothesis

A
  • CTVT not associated with low genetic diversity in dogs
  • CTVT not a major problem in inbred pops of wolves
  • Devils rejected skin grafts from MHC-similar devils
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12
Q

Conservation management of devils

A
  • Mainland zoos
  • Free ranging populations - offshore islands
  • Captive breeding program to maximise MHC diversity
  • -> first attempt t increase immunological fitness in captive population
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13
Q

Additional Issues

A

Devils changing behaviour

  • Very young age- structure populations in which females are reduced to single breeding (previously 3)
  • Compensation - 3 fold increase in females breeding in first year
  • Lead to semelparity in devils?

High phenotypic plasticity and evolutionary potential of DFTD
- allows to change its genetics and possibly behaviour

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14
Q

Semelparity

A

Reproductive strategy in which species is characterised by s single reproductive episode before death

e.g. Pacific salmon

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