naturebriefs
9:22in productionCh. 1 · Skin is the target/ 9:22 · ceiling 15 min
Fungi · Extinction

Batrachochytrium dendrobatidis

A cold-loving fungus that kills frogs by sabotaging their skin—and reshaped extinction science in the process.

Batrachochytrium dendrobatidis is a chytrid fungus that causes chytridiomycosis in amphibians. It infects keratinized skin. It disrupts osmotic regulation. This leads to cardiac arrest. Its zoospores are motile, chemotactic, and travel one to two centimetres. It thrives between 4–25 °C. Growth halts above 28 °C. It is found worldwide—from lowland forests to cold mountain tops. It has devastated amphibian populations since its 1998 discovery. It contributed to extinctions in the Holocene extinction. Some amphibians resist infection via symbiosis with Janthinobacterium lividum. Surviving populations may reflect evolutionary selection. It also infects crayfish—but not mosquitofish.

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Chapters & takeaways6
  1. 0:41
    Skin is the target

    It only infects amphibians—by binding to keratin in their skin.

  2. 1:39
    How it finds its host

    Its zoospores swim less than two centimetres—but chemotaxis makes them lethal at close range.

  3. 2:45
    Extinction and resistance

    It drove extinctions—but surviving populations hint at real-time evolution.

  4. 3:58
    What stops it

    Some frogs resist via bacterial symbionts; others survive through unconfirmed selection.

  5. 4:59
    The paradox of scale

    It spreads locally—not globally—yet caused worldwide collapse.

  6. 6:12
    A defining pathogen of our time

    It is a driver of the Holocene extinction—not a symptom.

Worth your time?

Yes. See the whole thing.

4.5/ 5
What works
  • targets keratinized amphibian skin
  • exploits osmotic regulation dependency
  • thermal limits match vulnerable habitats
What does not
  • infect mosquitofish
  • grow above 28 °C
  • spread over long distances
  • establish persistent environmental reservoirs beyond amphibian and crayfish hosts
See it if
  • epidemiologists
  • conservation biologists
  • evolutionary ecologists
Skip it if
  • naturalists seeking field identification
  • gardeners
  • pet keepers
The written brief1 min read

What the species is and where it came from

Batrachochytrium dendrobatidis is a chytrid fungus. It causes chytridiomycosis. It was discovered in 1998. It was described as a species in 1999.

How it works, in terms someone would actually use

It infects keratinized amphibian skin. It disrupts osmotic regulation. This leads to cardiac arrest. Its zoospores swim one to two centimeters. They use chemotaxis to find sugars, proteins and amino acids on amphibian surfaces.

What it gets right

It targets a universal amphibian vulnerability: keratinized skin. It exploits a conserved physiological dependency: osmotic regulation. Its thermal limits match high-elevation and temperate amphibian habitats precisely.

What it does not

It does not infect mosquitofish. It does not grow above 28 °C. It does not spread via air or water over long distances. It does not establish persistent environmental reservoirs beyond amphibian and crayfish hosts.

What it changed

It changed global amphibian conservation. It shifted focus from habitat loss to pathogen surveillance. It exposed limits of biosecurity in wildlife trade. It contributed to extinctions in the Holocene extinction.

Who it is for, and who it is not

It is for epidemiologists, conservation biologists and evolutionary ecologists. It is not for naturalists seeking field identification, gardeners, pet keepers or policy makers without amphibian mandates.

Is it worth your time

Yes—if you study amphibian decline, fungal ecology or disease-driven extinction. No—if you seek a species with observable behaviour, habitat specificity or direct ecological service.

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