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Fungi · Extinction

Batrachochytrium dendrobatidis

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

Worth your time?4.5/5Yes.See the whole thing.What works, what does not, who it is for ↓
9:22in productionCh. 1 · Skin is the target/ 9:22 · ceiling 15 min
6 chapters · 9:22Ceiling 15:00

The brief is written and checked. The video joins this page when it is cut.6 chapters · 1 min read · 9:22 planned

Read the brief

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.

FungiExtinctionDiseaseExtinctionEvolutionDisease across the network →
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.

3 more chaptersFewer chapters
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
Who should see it, and who should skipHide who it is for
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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9:41
Geastrum triplexGeastrum triplex is the largest earthstar fungus. It grows saprobically in hardwood forest detritus and leaf litter across Eurasia, Australasia and the Americas. Its immature fruit bodies are spherical and buried. Maturation involves exoperidial splitting into 4–8 rigid rays that lift the spore sac, exposing a gleba that transitions from white/firm to brown/powdery. A layer of the exoperidium often splits around the spore sac’s perimeter, forming a collar or saucer. The peristome is a small pointed beak atop the spore sac with a hole for spore release. It has documented use in traditional medicine (Blackfoot, Cherokee, Chinese) and contains bioactive sterols and fatty acids—but it is not considered edible due to toughness.
8:50
MyceliumMycelium is the vegetative, hyphal network of fungi. It functions as a nutrient-absorbing, decomposing, and symbiotic interface across terrestrial and aquatic ecosystems. It exhibits structural plasticity—from microscopic colonies to continent-scale networks—and mediates critical ecological processes including carbon cycling, plant nutrition via mycorrhizal associations, and bioremediation. Its biological functions—enzyme-driven extracellular digestion, electrical signaling, memory-like adaptive responses, and self-assembling adhesion—underpin emerging applications in construction, packaging, agriculture, and environmental engineering.
10:22
MorchellaMorchella is a genus of edible sac fungi in the order Pezizales (division Ascomycota), typified by Morchella esculenta in 1794. It exhibits a distinctive honeycomb cap morphology due to ridges and pits, and comprises over seventy molecularly supported species worldwide, most showing high continental endemism and provincialism. The genus is under active phylogenetic, biogeographical, taxonomic, and nomenclatural study, with new species recently described across multiple continents. Morels are highly valued in gourmet cuisine—especially Catalan and French—but are toxic when raw or undercooked. Commercial harvesting of wild morels constitutes a multimillion-dollar industry across the temperate Northern Hemisphere, including North America, Turkey, China, the Himalayas, India, and Pakistan. Their ecology remains poorly understood, though many species associate with trees symbiotically or saprotrophically, and some exhibit pyrophilic behavior, fruiting abundantly after wildfires. Cultivation has historically been difficult, though recent breakthroughs—including indoor cultivation using grass and climate control—have achieved reliable fruiting. Toxicity concerns include thermolabile hydrazine-based mycotoxins neutralized by cooking, and risks from environmental contaminants like lead and arsenic in certain habitats.
9:54
Amanita muscariaAmanita muscaria is a basidiomycete fungus native to temperate and boreal forests of the Northern Hemisphere, now naturalised in the Southern Hemisphere. It forms ectomycorrhizal symbioses with trees. It contains muscimol and ibotenic acid, causing variable, rarely fatal intoxication. Parboiling reduces toxicity; drying converts ibotenic acid to muscimol. Its name may derive from fly-killing use or delirium-inducing effects. Genetic diversity suggests it is a species complex. Some cultures use it as food after preparation.
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