Amphibian extinction by fungi: ecological consequences and protective measures
Every third frog is threatened
Every third frog, salamander and every third toad in the world 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.
165 species already extinct
However, the greatest danger comes from the chytrid fungus batrachochytrium dendrobatidis. He has been diagnosed since 1999, is believed to come from Africa and triggers the largest extinction of modernity in the shortest possible time. Since 1980, probably 165 species of frogs, toads, newts and salamanders have died, 435 migrated to a higher category of endangerment.
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In Ecuador, for example, the country with the highest biodiversity of amphibians, 156 of the more than 700 species of frogs today are dying outThreatened - 16 the mushroom has already gathered there. So far, especially South and North America like Australia have been affected.
Highly endangered by the fungus 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 layer of the animal's skin, which subsequently dies within a few weeks.
Hundreds of species are unlikely to survive in their natural habitat and need short-term breeding stations in human care that are 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 spotted toad
The Kihansi spotted toad eliminated the mushroom in the wild in 2009. She lived in the Kihansi Falls in Tanzania. In this particular place, however, it was very common, estimates came from 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 in Panama died in human care in the US in 2016.The fungus had extinguished the species in the wild in a few years' time.
The global conservation organization IUCN demands that all amphibian species, which are critically endangered in nature, be systematically cultivated in human care. Zoos and aquariums should also work with qualified private owners.
In fact, most of the amphibian species can easily be cultured under human care with today's technical capabilities, and that on a much smaller scale than, for example, endangered large mammal species.
In addition, most amphibians produce a lot of spawning, since 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
Since 2005, the World Association of Zoos and Aquariums has developed a program called the Amphibious Ark.
The vertices are the following:
Each zoo and aquarium should participate as much as possible in the amphibian protection program. This may include:
informing visitors about the dangers that amphibians are exposed to today through appropriately designed exhibits and information panels in the zoo or aquarium.
Theming of amphibian protection in the context of zoo lessons.
Informing the general public through press releases, the Internet, etc.
Create the human and spatial conditions to keep amphibians in larger numbers and to breed them as part of long-term programs.
Ecological enhancement of the zoo area to create habitats for native amphibians.
Protecting 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
Meanwhile, some extremely endangered species have not only been raised in human care, but have been re-exposed in fungus-free areas. So the Spotted Tree Frog 2001 in the central highlands of Victoria, Australia, in the wild became extinct.
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. 16 years later, he poached offspring in a remote area of the national park, which will most likely remain free of 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 thus 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.
The fire salamander
Batrachochytrium dendrobatidis( Bd) has a relative: Batrachochytrium salamandrivorans( Bsal).The struck in recent years at 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 burbot grows in cool streams as well. The salamanders die because the fungus alters the top layer of skin, causing ulcers.
Private storage of amphibians is prohibited in the Netherlands. What first speaks for a particular awareness of conservation is now proving counterproductive, as the Dutch can not rely on private resources to preserve the salamanders.
Nine out of Ten Animals Die
Experience with the killer fungus teaches above all: 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 animal disease control 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 infected 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 Africa and Africa 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 may have 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.
Was the fungus 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 stocks of salmon-free salamanders in Guatemala declined massively in the 1980s, although their habitats remained undisturbed.
researchers noted 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 that do not target large areas of water and even lay their eggs in the small accumulations of rainwater that form in the leaf hoppers of bromeliads.
Why are fungi dangerous to 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 liquid like minerals and excrete waste. Lungless salamanders even breathe through the skin.
When the chytrid fungus infests the animals, keratin clogs the pores and suffocates the amphibians. However, Batrachochytrium salamandrivorans does not appear 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 inferred from ox frogs in captivity, who were in good health and the fungus could not harm.
Strengthening the immune system
Researchers at the James Madison University made a discovery that gives hope. Salamanders 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 vulnerable, this could slow down the spread of the pathogen.(Dr. Utz Anhalt)
The Amphibian Apocalypse - Mushroom Causes Mass Dying
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.
This would have ecological consequences that 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.
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The amphibious apocalypse - fungus causes mass extinction
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