The dramatic situation
Declining amphibian populations is a global phenomenon. Amphibians are currently considered the most threatened group of vertebrates on the planet, which are suffering some of the largest extinctions in the world. The main causes are a combination of local and global factors and all can be attributed to human impacts on the environment that directly or indirectly cause a loss of forest quality and thus its vital functions, such as climate change, destruction and transformation of habitats, introduction of non-native species, farming practices and in the last decades a new threat has been added: the irruption of emerging diseases such as chytridiomycosis and Ranavirus, which can cause the disappearance of populations in a few months.
Chytridiomycosis is an infectious disease that affects amphibians around the world. It is caused by the Chytrid Fungus (Batrachochytrium dendrobatidis). This silent killer has slaughtered amphibians around the world, for decades. In the 1980s, it started to devastate frog populations worldwide, and now it is considered the greatest catastrophe of biodiversity in terms of diseases, in our history
There are hundreds of species of chytrid fungi, and most of them are unobtrusive decomposers. But Batrachochytrium dendrobatidis has a special taste for the proteins in amphibian skin. The fungus kills amphibians by degrading the keratin in their skin, making it harder for them to absorb the oxygen and trace minerals they need for good health and, in turn, causing heart failure. It basically eats their skins alive.
Not only is this fungus lethal, it’s also devastatingly effective at spreading. Along the way, it evolved, spawning a highly virulent strain that’s primarily responsible for the pandemic. The fungus can spread by contact or by water; and its spores can swim a short distance. And if conditions are right, the fungus can live outside of its host for weeks or even months.
This fungus was and even today is spread around the globe, mainly by the international wildlife trade
Declines in amphibian populations bear significant implications for the functioning of many ecosystems, and as humans, we will suffer the consequences of it, and the same way with the decline of the rest of the Earth’s biodiversity worldwide.
It’s like a Domino effect, when you remove or affect one or a group of living beings, this triggers a cascading effect that affects other life groups. And at the end this affects the functioning of the entire ecosystem.
A recent research in Panama has shown that populations and body size of tropical snakes are being affected by the disappearance of amphibian populations
Amphibians are amazing creatures.
Amphibians were the first group of vertebrates that developed legs and managed to get out of the water to conquer the land. Although they are generally considered by most to be simple and primitive animals, amphibians display a high diversity of survival strategies that have allowed them to occupy a large part of terrestrial and freshwater habitats.
Amphibians are small vertebrates that need water, or a moist environment, to survive. The species in this group include frogs, toads, salamanders, caecilians and newts. All can breathe and absorb water through their very thin skin.
Amphibians also have special skin glands that produce useful proteins. Some transport water, oxygen, and carbon dioxide either into or out of the animal. Others fight bacteria or fungal infections. And at least one, in each species, is used for defence.
Evolution allowed amphibians, like other animals, to develop strategies for survival. Some of them developed the ability to go unnoticed both to their predators – in some cases – and to their preys – in others. This capability, which allows many of them to complete their life cycle, is called crypsis or cryptic coloration, and gives the individual the power to blend in with their surroundings.
In this design trial, nature allowed some toxic or poisonous amphibians, to have bright colors and flashy designs; these are warning colors, a strategy called aposematism. Instead of going unnoticed, they warn potential predators that they are preys unpleasant to eat, with bad taste or poisons. Eventually, predators learn that some combination of colors produce an unpleasant experience, and then they avoid repeating it. Bold, bright colors, like a traffic light, mark danger and need to stop.
And in this skill of simulation, mimicry appears, which happens when an animal copies another one’s strategy, using it as a model. It is, for example for the case of animals that are not poisonous, wherein they mimic the coloration of those who are, avoiding predators by making them believe they are unfit for consumption, or dangerous.
In amphibians, body temperature varies with ambient temperature. They are ectotherms, meaning they can only rely on external sources of energy to regulate their temperature. In this incredible explosion of creativity Nature allows a frog adapted to extreme cold temperatures (the Alaskan Wood Frog) generate a strategy that prevent this freeze-pop effect by packing their cells with glucose (a kind of sugar) that reduces drying and stabilizes cells, a process scientists call cryoprotection. Concentrating sugar inside the cell helps balance the concentration of salts outside the cell that occurs as ice forms.
Language is one of the most complex tools with which beings can exchange experiences and share the perception of their environment. Just as humans use a wide and sophisticated order of phonemes, frogs and toads produce a rich variety of sounds, calls, and songs during their courtship and mating rituals. The callers, usually males, make stereotyped sounds in order to communicate their location, their mating readiness and their willingness to defend their territory; listeners respond to the calls by returning the call, by approaching and by going silent. These responses have been shown to be important for species recognition, mate assessment, and localization. Pheromonal communication is widespread in salamanders and newts and may also be important in some frogs and toads.
Final thoughts
There are currently more than 7700 recognized species of amphibian and new species are being added to the list each month, especially in the tropical areas. This is either due to new species discoveries or as a result of taxonomic revisions where a taxonomic split of one previously recognized species results in several new species.
But the situation of conservation is critical, amphibians have existed on earth for over 300 million years, yet in just the last two decades there have been an alarming number of extinctions; nearly 168 species are believed to have gone extinct and at least a 43% more have populations that are declining. This indicates that the number of extinct and threatened species will probably continue to rise.
That’s why researchers and conservationist are urging governments around the world to pay attention to this problem by curbing the trade of wild amphibians, protecting amphibian habitats, combating invasive species that threaten amphibians, and supporting captive-breeding programs.
Conservation of each being is essential to ensure the existence of an intricate network supported by complex relationships, which allow the fragile balance of life and, therefore, our existence. This could be enough to consider their protection; however, there is another aspect that adds importance to conservation: the intrinsic value of life. That is, that it exceeds expressions based on valuations for the human being, to open scenarios in which the manifestation of life is a value in itself.
References
https://science.sciencemag.org/ content/367/6479/814
https://www.researchgate.net/ publication/273765761_Presence_of_amphibian_ chytrid_fungus_Batrachochytrium_dendrobatidis_ in_rainwater_suggests_aerial_dispersal_is_ possible/link/556c49e108aeab7772217ae4/ download
https://science.sciencemag.org/ content/363/6434/1459
https://www.researchgate.net/publication/26411061
https://www.the-scientist.com/notebook/ researchers-fight-a-devastating-amphibianinfection-using-heat-66905
https://www.environment.gov.au/system/ files/resources/279bf387-09e0-433f-89733e18158febb6/files/c-disease_1.pdf
https://www.researchgate.net/ publication/44652493_Pheromonal_ communication_in_amphibians
