Amphibian Chytrid Fungus

The amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) is a microscopic fungus that infects the skin of amphibians and has caused the greatest documented loss of biodiversity attributable to a disease. It has been implicated in the decline of hundreds of amphibian species, including dozens presumed extinct.

🧬 Field Guide Specimen: Open Amphibian Chytrid Fungus in the CRV Science Field Guide to log the specimen, see its place among the Opisthokonta lineages in the Cladogram Explorer, and test your recall in the Red List conservation game.

The fungus grows in the keratin-rich outer layer of the skin. Amphibians breathe and take up salts through the skin, and heavy infection disrupts the transport of sodium and potassium, which can lead to cardiac arrest. Motile zoospores with a flagellum spread in water.

A 2019 analysis counted about 500 species that have declined because of the fungus, 90 of which are presumed extinct. Genetic evidence points to East Asia as the origin of the pandemic lineage, spread by the international trade in amphibians for pets, food and research, such as the African clawed frog and the American bullfrog.

Some frogs show resistance, and skin bacteria that make antifungal compounds provide protection. Conservation efforts include captive "ark" populations, probiotic treatments and warming of treated frogs, since the fungus is sensitive to heat.

• American Bullfrog — a tolerant carrier
• African Clawed Frog — an early carrier
• Fire Salamander — a victim of the related Bsal