amphibian chytridiomycosis
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What is amphibian chytridiomycosis?
Amphibian chytridiomycosis is a disease that affects amphibians, especially frogs, and is caused by the fungus Batrachochytrium dendrobatidis. This fungus infects the superficial layers of the epidermis, resulting in degradation of the skin and disruption of gas exchange, which eventually leads to cardiac arrest. It has been implicated in the extinction or population decline of many amphibians around the world and is considered an exotic or invasive species in most areas. The disease is now pandemic, with the fungus having infected over 500 species.
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Which types of amphibians are affected by chytridiomycosis?
Chytridiomycosis is a disease caused by the fungus Batrachochytrium dendrobatidis that affects amphibians, especially frogs. This disease has been implicated in the extinction or population decline of many amphibians around the world and is considered an exotic or invasive species in most areas.
Batrachochytrium dendrobatidis has infected members of more than 500 species. The disease has decimated amphibian populations around the world and has caused the extinction of several species of frogs so far. For example, the Panamanian golden frog has suffered heavily from the disease.
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What causes chytridiomycosis in amphibians?
Amphibian chytridiomycosis is a disease that affects amphibians, especially frogs, and is caused by the fungus Batrachochytrium dendrobatidis. This fungus infects the superficial layers of the epidermis, resulting in degradation of the skin and disruption of gas exchange, which eventually leads to cardiac arrest.
The origin of B. dendrobatidis is believed to be from the Korean peninsula, emerging in amphibian populations between 1898 and 1962. From there, it spread globally through food and pet trading networks. Once introduced to an area, it spreads rapidly between amphibians via infectious reproductive cells called zoospores.
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How does chytridiomycosis harm amphibians?
Amphibian chytridiomycosis is a disease caused by the fungus Batrachochytrium dendrobatidis that harms amphibians, especially frogs. The fungus infects the skin's superficial layers, causing skin degradation and disrupting gas exchange. This leads to an imbalance in blood chemistry and, eventually, cardiac arrest due to reduced sodium and potassium concentrations.
The disease has led to significant population declines and extinctions in hundreds of amphibian species worldwide. Once introduced to an area, the fungus spreads rapidly via infectious reproductive cells called zoospores. These zoospores encyst on the skin, penetrate epidermal cells, and grow into mature thallus, releasing more zoospores and continuing the infection.
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How has chytridiomycosis affected amphibian populations around the world?
Amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis, has led to significant declines and extinctions among amphibian populations worldwide. The disease disrupts gas exchange and electrolyte balance, leading to cardiac arrest.
Originating in Korea, the fungus spread globally through trade networks. It infects over 500 amphibian species and is present on all continents except Antarctica. In Panama, infection by Batrachochytrium dendrobatidis affected 52 out of 70 amphibian species, causing a 90% reduction in amphibian density. The decline in frog populations has also triggered a drop in snake biodiversity, highlighting the wider ecological implications.
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What can scientists and conservationists do to prevent and treat chytridiomycosis?
Amphibian chytridiomycosis is a disease caused by the fungus Batrachochytrium dendrobatidis (Bd), impacting frogs and other amphibians globally. The infection degrades the skin, disrupts gas exchange, and can lead to cardiac arrest.
To combat this, conservation efforts include captive breeding programs, like Project Golden Frog, which aim to preserve species and reintroduce them with resistance to the fungus. Scientists are also studying the disease to find ways to prevent its spread and treat infected amphibians.
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amphibian chytridiomycosis, a disease affecting amphibians, especially frogs, caused by the fungus Batrachochytrium dendrobatidis. B. dendrobatidis, known among herpetologists as the amphibian chytrid or simply Bd, has been implicated in the extinction or population decline of many amphibians around the world. The fungus was formally described in 1999 after it was isolated from infected captive poison frogs (such as the South American poison-arrow frog, Dendrobates auratus). It was the first chytridiomycete fungus known to infect vertebrates—its closest relatives being saprophytic fungi (that is, fungi that live off of dead matter) and other fungi that infect algae, plants, and invertebrates. At present, the disease is pandemic, and the fungus is regarded as an exotic or invasive species in most areas.
Early investigations into the disease suggested that Bd originated in populations of platanna (Xenopus laevis), an African clawed-frog species widely used in biological research. Evidence remained inconclusive until 2018, when a genomic study indicated that Bd had originated in a particularly diverse hot spot in the Korean peninsula, which contained several strains of the disease. Bd likely emerged in amphibian populations there sometime between 1898 and 1962 before spreading to other parts of the world through global food and pet trading networks.
Although humans likely cause the long-distance movement of Bd, once it has been introduced to an area, it spreads rapidly between amphibians by means of free-swimming infectious reproductive cells called zoospores. Once a zoospore has encountered a potential host, it encysts upon the surface of the skin and penetrates one of the host’s epidermal cells. Then the zoospore grows into a mature thallus that ultimately releases 40–100 zoospores over its 4–5-day life cycle. In species where Bd is highly pathogenic, as in those belonging to the genus Atelopus, the infection may cover most of the epidermis. As the skin degrades, gas exchange with the environment and electrolyte balance are disrupted. The infected animals eventually succumb to cardiac arrest due to significant reductions in sodium and potassium concentrations in their blood plasma.
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Bd has become a global threat to amphibian biodiversity. According to published reports, it has infected members of more than 500 species. The International Union for Conservation of Nature (IUCN) has declared only 35 amphibian species as formally extinct since 1500 ce; however, some 130 additional species are presumed to have gone extinct in the wild since 1980. Approximately 90 of these modern extinctions have been attributed to Bd. Since most documented population declines and extinctions have occurred in either temperate or tropical montane regions, Bd is thought to survive and grow best under cool, moist conditions. In addition, it has appeared in habitats ranging from rainforest to desert, and it is present on all continents except Antarctica.
At local scales, Bd can have devastating effects on amphibian communities. For example, in El Cope, Panama—where Bd has been conclusively shown to infect local amphibian species—the disease occurred in 52 of the 70 described amphibian species in the area and caused a 90 percent reduction in overall amphibian density. Many experts suspect that Bd is at the root of similar damage at many other sites (such as Monteverde, Costa Rica, and the rainforests of Queensland, Australia), though it has not been proved to be the cause.
Evidence of the wider ecological implications of falling amphibian populations caused by Bd infection came to light in 2020. Frogs and other amphibians in the tropics are important food sources for snakes. A 2020 study that examined herpetological biodiversity in Panama noted that the rapid decline of frog populations there triggered a drop in snake biodiversity overall and reduced health among many surviving snake species (see also trophic cascade).