32 harlequin species were thought to be extinct, but they were just hiding from zoologists

(ORDO NEWS) — Here is the star harlequin (Atelopus arsyecue) – a small toad that lives only in the Sierra Nevada de Santa Marta mountain range in northern Colombia.

Zoologists first discovered this beautiful amphibian in 1991, and haven’t seen it in nearly thirty years since. Experts even feared that the stellar harlequin had died out.

However, the locals knew that a population of this species still existed. In 2016, they shared fresh pictures of these toads with scientists – and in 2019 they allowed them to see them with their own eyes.

This is not the first and not the last representative of the Atelopus genus, which was considered extinct, but then “resurrected”.

For example, in 2016, the harlequin toad A. ignescens, which had not been seen since the late 1980s, was rediscovered in Ecuador.

But how did zoologists manage to rediscover these species? And why were so many harlequins thought to be extinct? Let’s figure it out.

If you read the previous issue of our frog blog, you already know about the deadly fungus Batrachochytrium dendrobatidis, which spread widely around the world and at the end of the last century caused a massive pestilence among American, Australian and European tailless amphibians.

However, the dangerous infection spread unevenly.

The fact is that B. dendrobatidis does not tolerate heat, therefore it settles mainly in mountain forests and mountain tundra, where the air temperature ranges from 17 to 25 degrees Celsius. Amphibians living in such places suffered from the fungus in the first place.

Most species of harlequin toads live along the banks of mountain streams from Costa Rica to Bolivia. Not surprisingly, they were particularly hard hit by the outbreak of chytridiomycosis.

Zoologists know about a hundred species of the genus Atelopus – and at least seventy percent of them have been reduced in numbers due to a deadly fungus so much in recent decades that they are endangered.

Most of these species (as well as some other species of the genus that have not yet received a scientific description and conservation status) have not caught the eye of scientists for 10-40 years. It is highly likely that many of them are completely extinct.

Although harlequins face other problems, such as deforestation and pollution, experts have no doubt that B. dendrobatidis should be blamed for their rapid extinction.

To appreciate the scale of the disaster, just open Wikipedia and look at the list of species of the genus Atelopus. It is easy to see that most of them are on the verge of extinction or may have disappeared.

Only a few species of harlequins have not yet been included in the list of threatened, for example, A. spurrelli from the slopes of the Western Cordillera in Colombia.

Despite the fact that people have put many species of living organisms on the brink of survival, the situation of most groups is not as difficult as that of harlequins.

They can only be compared with Hawaiian flower girls (more than half of the approximately 50 species of these birds became extinct due to the fault of humans and invasive species) and land snails from the Pacific Islands belonging to the families Partulidae and Achatinellidae (most of their species were exterminated by predators introduced by people).

The rapid extinction of harlequin toads upsets herpetologists and all wildlife lovers, because many species of these amphibians are distinguished by bright colors and unusual mating rituals.

For example, male harlequins (they are inferior to females in size), having found a potential partner, sit on her back and ride her for a long time, sometimes up to several months, waiting for the start of the mating season. So they isolate it from competitors.

The maximum period during which a male harlequin can keep a female is characteristic of the species A. laetissimus, which has not yet disappeared, and is 138 days. In addition, harlequins are important for mountain forest and paramos ecosystems.

The fact is that these amphibians regulate the number of invertebrates, and they themselves – as well as their eggs and tadpoles – serve as food for other living creatures. In the past, some species of harlequins reached very high numbers: for example, thousands of A. ignescens individuals could be seen after rain on paramos in the Ecuadorian Andes.

The near extinction of these numerous populations reduced the productivity of ecosystems and harmed the flow of energy between land and water.

However, zoologists, of course, did not sit back and just watch how harlequin toads disappear from the face of the Earth. Some species of these amphibians managed to survive in captivity.

Thanks for this should be specialists who caught enough individuals of each such species in time to create safety populations outside their natural ranges. By the time such species finally disappeared in nature due to the fungus, they had already been successfully bred in captivity.

This happened, for example, with the harlequin Tsetek (A. zeteki) from Panama. In nature, this beautiful species, apparently, has become extinct, but has been preserved in zoos and nurseries.

In addition, scientists regularly organize expeditions to the most remote regions of Central and South America in the hope of discovering surviving populations of harlequins teetering on the brink of survival. And these searches often end successfully.

Since the turn of the 21st century, a team of zoologists led by Kyle E. Jaynes of the University of Michigan calculated that 32 species of harlequins that were thought to be extinct after the outbreak of chytridiomycosis have been rediscovered since the beginning of the 21st century, including the already familiar A. arsyecue and A. ignescens.

This is about 37 percent of the total number of lost species of these amphibians (including undescribed species). For example, in Ecuador, populations of more than half of the native species not observed since the outbreak have been rediscovered in recent years.

It is possible that at least some of the rediscovered harlequin species have adapted to the presence of B. dendrobatidis.

These amphibians mostly live at the same altitudes as before the mass death of their relatives, that is, they did not just hide from the fungus in unsuitable conditions for it.

And on the skin of some harlequins belonging to rediscovered species, researchers found traces of B. dendrobatidis – but the infection no longer seemed to harm them.

Janes et al. warn that even “resurrected” harlequins remain seriously endangered. Most of them are much lower than before the outbreak.

In addition, as the analysis carried out for six species showed, the rediscovered species have lost a significant part of the genetic diversity, which may adversely affect their survival.

They probably come from a small number of individuals who were able to survive the mass death of relatives due to the fact that they were less susceptible to the fungus or were able to protect themselves from it in some other way.

What will be the fate of the rediscovered harlequins and how many more missing species of these amphibians zoologists will be able to find (and there are still about fifty to be found), only time will tell.

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