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Amphibian death by fungi Ecological consequences and protective measures
The amphibious apocalypse - fungus causes mass extinction
For the first time in human time on the planet, an entire class of vertebrates is threatened with extinction. The amphibious death is on the rise.
That would have ecological consequences, which we can not even estimate. The unchecked multiplication of insects that transmit dangerous diseases is just one of them, the loss of one essential food source for countless bird species another. The apocalyptic riders for the amphibians are habitat loss, environmental toxins such as pesticides and climate change. Add to that an old adversary who is as deadly as ever.
contents
- The amphibious apocalypse - fungus causes mass extinction
- Every third frog is threatened
- 165 species are already extinct
- The Gischtkröte
- breeding management
- The amphibious ark
- Spotted Tree Frog back in the wild
- The fire salamander
- Nine out of ten animals die
- The midwife toad
- How did the fungus spread??
- Was the fungus already deadly before?
- Why are mushrooms dangerous for amphibians??
- Strengthen the immune system
Every third frog is threatened
Every third frog, salamander and every third toad worldwide are on the red lists of endangered species. The stocks of amphibians are exposed to thousands of damage anyway - their habitats disappear, the pollution of the environment is particularly important to them. They are very sensitive to climate change because, unlike warm-blooded animals, they are directly dependent on specific temperature and humidity.
Frogs, toads or salamanders: Many amphibian species worldwide are threatened with extinction.(Creativenature.nl/fotolia.com)
165 species are already extinct
The greatest danger, however, comes from the chytrid fungus batrachochytrium dendrobatidis. He has been diagnosed since 1999, probably comes from Africa and triggers the largest extinction of modernity in the shortest time: Since 1980 probably died 165 species of frogs, toads, newts and salamanders, 435 migrated to a higher category of endangerment.
For example, in Ecuador, the country with the highest biodiversity of amphibians globally, 156 out of more than 700 frog species are threatened with extinction today - 16 the mushroom has already gathered there. So far, especially South and North America like Australia have been affected.
The fungal species most at risk are highly specialized species, such as the Kihansi gull toad, which live in a particular biotope in a small area and have historically only seen a few individuals. But the mushroom also easily extinguishes former Allerweltsarten. The waterborne pathogen infects the upper skin layer of the animals, which then die within a few weeks.
Hundreds of species are unlikely to survive in their natural habitat and will require short-term breeding stations in human care, free of the fungus, so as not to divide the fate of the dinosaurs, and to re-develop free-range populations in the long term.
The Gischtkröte
The Kihansi gull toad eliminated the mushroom in the wild in 2009. She lived in the Kihansi Falls in Tanzania. However, it was very common in this particular place, with estimates of 17,000 adult animals.
A dam, which reduced the amount of water to one tenth, led to a massive collapse of the stock. Then came the mushroom and with it the end for the toad. Today the Gischtkröte only lives in a few zoos.
The last Rabb tree frog from Panama died in human care in the United States in 2016. The fungus had extinguished the species in the wild in a few years' time.
Conservationists demand systematic breeding under human protection for all endangered amphibians. (Image: hydebrink / fotolia.com) breeding management
The global conservation organization IUCN demands that all amphibian species that are critically endangered in nature be systematically cultivated in human care. Zoos and aquariums should also work together with qualified private owners.
In fact, most of the amphibian species can easily be grown in human care with today's technical possibilities, and that on a much smaller area than, for example, endangered large mammal species.
In addition, most amphibians produce a lot of spawning, as in nature, most tadpoles and juveniles are predators of predators. Assuming a coordinated network of breeders, populations in captivity can grow rapidly as many of the juveniles survive.
The amphibious ark
The World Association of Zoos and Aquariums has been developing a program since 2005, the Amphibious Ark.
The cornerstones are the following:
Each zoo and aquarium should participate as much as possible in the amphibian protection program. This can include the following measures:
- Informing visitors about the dangers that amphibians are exposed to today through appropriately designed exhibitions and information boards in the zoo or aquarium.
- Topic of amphibian protection in the context of zoo lessons.
- Informing the general public about press releases, internet, etc.
- Create the personal and spatial conditions to keep amphibians in larger numbers and to breed in long-term programs.
- Ecological enhancement of the zoo area to create habitats for native amphibians.
- Caring for protected areas or participating in actions to protect the local amphibian fauna.
- Supporting zoos, aquariums and conservation agencies in developing countries with high amphibian biodiversity through knowledge transfer and provision of husbandry facilities and other material.
- Participation in research and protection projects in developing countries.
Spotted Tree Frog back in the wild
In the meantime, some extremely endangered species have not only been cultured in human care, but have been re-exposed in fungus-free areas. In 2001, the Spotted Tree Frog was extinct from the central highlands of Victoria, Australia, in the wild.
Dr. David Hunter of the NSW Office of Environment and Heritage led the team that captured the last tree frogs in the Kosciuszko National in 2001 to build a protected population.
Sixteen years later, he poached offspring in a remote area of the national park, which will most likely remain free of the fungus. Hunter says the frogs are a key in the food chain because they provide a resource for reptiles, birds and mammals.
The new home of the frogs is warmer and drier than their usual habitat and therefore unsuitable for the fungus, as it does not like temperatures above 28 degrees. So far, more than half of the abandoned frogs survived, and the animals continued to breed.
A highly infectious chytrid fungus has left the fire salamander in the Netherlands almost extinct today. (Image: Karl Lugmayer / fotolia.com) The fire salamander
Batrachochytrium dendrobatidis (Bd) has a relative: Batrachochytrium salamandrivorans (Bsal). The struck in recent years in the fire salamanders in the Netherlands. Of these, probably only 4% survived the infestation since 2010.
The related species needs colder temperatures and dies already at 25 degrees Celsius. Unfortunately, fire salamanders prefer cool forest areas, and their tadpoles also grow in cool running waters. The salamanders die because the fungus alters the top layer of skin, causing ulcers.
In the Netherlands private ownership of amphibians is prohibited. What first speaks for a particular awareness of nature conservation, now proves to be counterproductive, since the Dutch can not rely on private stocks to obtain the salamanders.
Nine out of ten animals die
Above all, the experience with the killer mushroom teaches that even a small amount of the highly infectious fungus could destroy the entire population of fire salamanders in Western Europe. Within six months approximately 90% of the animals die in an infected population.
In both variants of the fungus, the classical means of combating animal diseases fail: Neither vaccination nor repopulation are possible, and the fungus can not be removed from the biotopes.
The midwife toad
The midwife toad of Western Europe also suffers from the fungus. It is possible that humans have spread the mushrooms with their shoes, because the affected animals found themselves increasingly near hiking trails. In the Iberian Peninsula, more than a quarter of midwife toads suffer.
How did the fungus spread??
The fungus probably spread in America and Australia with African clawed frogs. These have been used since the 1930s for pregnancy tests, as the urine of pregnant women injected into the skin, causing the females to develop eggs.
Furthermore, the worldwide trade in terrarium animals probably spread the fungus. Even with frogs and toads in private life, he is now the leading cause of death. The European Erstnachweis took place in 2000 with poison dart frogs, which were imported fresh from Costa Rica.
In Europe, the fungus was first detected in 2000. The affected animals were poison dart frogs imported from Costa Rica. (Image: Michael Stifter / fotolia.com) Was the fungus already deadly before?
The fungus has existed for millions of years, and it is still unclear whether he was responsible for the amphibian deaths of the past. For example, the numbers of salmon-free salamanders in Guatemala declined massively in the 1980s, although their habitats remained undisturbed.
Researchers found that this decline coincided with the spread of chytrid fungus. So he appeared in the early 1970s in Mexico, shortly thereafter in southern Guatemala and 1987 in Costa Rica - and there were local incursions of amphibian populations everywhere.
The hypothesis is that the fungus has always existed in the environment. With climate change, the cold-loving pathogen was able to spread. However, it remains unclear how the aquatic fungus could infest amphibians of the rainforest, which do not target large bodies of water and even lay their eggs in the small accumulations of rainwater that form in the leaf hoppers of Bromeliads.
Why are mushrooms dangerous for amphibians??
Fungal attack of the skin is unpleasant for humans, in amphibians it threatens the life. Because frogs, toads and salamanders take on the skin fluid like minerals and excrete waste. Lungless salamanders even breathe through the skin.
If the chytrid fungus infests the animals, keratin clogs the pores and suffocates the amphibians.
However Batrachochytrium salamandrivorans does not seem to kill amphibians with a stable immune system. However, if other pathogens, a change in the climate and stress, the disease breaks out. This can be concluded from ox frogs in captivity, who were in good health and the fungus could not harm.
Strengthen the immune system
Researchers from James Madison University made a discovery that gives hope. Salamander and many frogs naturally have a defense against the chytrid fungus in the form of bacteria on their skin and skin proteins.
Scientists suspect that multiplying these beneficial bacteria could reduce contagion and start the immune system. One idea is to make amphibians in human custody more resistant to the pathogen in order to expose these starched animals in the wild. If the animals were less susceptible, this could slow down the spread of the pathogen. (Dr. Utz Anhalt)