November 26, 2020

The lord of amphibians | Science

The lord of amphibians | Science


During a good part of 2018 and until February 14, Romeo, a male who was believed to be the only living specimen of a frog from Sehuencas (Bolivia), had a great media role because almost in extremis several were found juliettes of its same species. However, in almost no information was highlighted the role of a Spanish researcher, Ignacio de la Riva, who found and described the species at the end of the last century and is a direct witness of one of the greatest recent declines in the animal kingdom: the Amphibians

"In the same area of ​​Bolivia where I discovered and described the Sehuencas frog (Telmatobius yuracare) there are other species of the same genus that have disappeared. It's over. They were described at the end of the last century and the beginning of this and they are now considered missing. " Ignacio de la Riva, scientific researcher of the Superior Council of Scientific Research in the National Museum of Natural Sciences (MNCN / CSIC), talks about the terrible drama that lies behind the mediatic case of Romeo, with which, by the way, the first mating attempt with the happily found females that wanted it to coincide with Valentine's Day was frustrated.

Already in 2006, together with his colleague Jaime Bosch also of the MNCN / CSIC, alerted in EL PAÍS about the cause of this devastation, a fungus called Batrachochytrium dendrobatidis that causes the disease of chytridiomycosis. Bosch and De la Riva were part of the group of researchers that in 1998 certified the first case registered in Europe. It was in the Sierra de Guadarrama (Madrid), and more specifically in the Peñalara lagoons, where they found an abnormal absence of common midwife toad larvae. "The mushroom chytridium it is more pathogenic in a temperature range no higher than 23 degrees, and in Europe it affects mainly mountain species, but it is very widespread in the rest of the continents ", explains the herpetologist, who also remembers that the alarm voice On the global decline of amphibians occurred in 1989, during the first World Congress of Herpetology.

If in the information of 2006 the amphibians already appeared as the class of vertebrates with greater presence in the Red List of Endangered Species of the International Union for the Conservation of Nature, with 32% of their species in the list, the situation has worsened significantly and now they are 41%, and climbing. They are the class of vertebrates that contributes more species (551) to the category of "critically endangered", close to fish, which have 485, but with the exception that around 30,000 species of fish are recorded in the world and 8,000 amphibians.

It is rare to start reading the causes of constant regression of some of these 551 randomly chosen species and not to give in the chips with the words chytrid fungus or chytridiomycosis, English terms of fungus and disease, respectively. Ignacio de la Riva, excited by what he found on his first visit to the discovery site of the Sehuencas frog and disillusioned with the shortages he found when he returned shortly after, has been dedicated in recent years to investigate this threat. He even detected one of the greatest experts in the infection, Patricia Burrowes, of the University of Puerto Rico, the oldest known record of the disease.

It happened while they were reviewing the amphibian collection corresponding to the Pacific Scientific Commission, the main ultramarine scientific expedition of the Elizabethan Spain, carried out between 1862 and 1866, and which had six professors linked to the MNCN. "There already appeared an infected copy of chytridiomycosis; in particular, we detected it in a giant frog from Lake Titicaca in Bolivia that was captured in 1863. Earlier, specimens with infections in Japan dating from 1901 and South Africa in 1938 had appeared, for example, "De la Riva reports.

But what removed him in his insides was the case of the Sehuencas area, where he found the first copy of Telmatobius yuracare: "In the first days of January 1990 I traveled with colleagues from the Noel Kempff Museum of Santa Cruz de la Sierra and two friends from Spain to various places along the Andes of Santa Cruz and Cochabamba, entering the valley of Sehuencas. It was a lush and pristine cloud forest, where no herpetologist had ever collected. In a river that crossed the road, with impressive waterfalls upstream, one of my friends (Jesús Dorda, also of the MNCN) saw a frog jumping into a small pool ".

It was a great male specimen of what De la Riva immediately identified as a new species of Telmatobius. "I've never seen any that had such humeral spines, which protruded from the front of the arm." In the following months, he collected new specimens and tadpoles in three locations distant from each other 140 kilometers. In July 1990 he counted 86 individuals in less than a kilometer of river in one of those locations (El Cañadón). And the disappointment came: "it was a very common species, but in another visit in 1994 I found nothing there; neither adults, nor juveniles nor tadpoles, neither of this species nor of another new one that I also found in the first visit, Telmatobius espadai"

Amphibians are the class of vertebrates that contributes more species (551) to the category of "critically endangered"

Fortunately, the case of Romeo and their juliettes has shown that isolated specimens remain in at least one other location and that a thread of hope for the survival of the Sehuencas frog is maintained. The opposite is true for T. edaphonastes Y T. sibiricus, also described by Ignacio de la Riva: "they have not been seen since 1998 and 2003, respectively". He does not hesitate to point to chytridiomycosis as responsible for this hecatomb, but also denounces that, at the same time that the president of Bolivia, Evo Morales, was satisfied with the finding of the juliettes, "The valley of Sehuencas is being destroyed by the construction of a hydroelectric dam and the infrastructures that accompany it, promoted by the Bolivian government; a dramatic contradiction. "

In total, this researcher of the MNCN has discovered and described seventy new species of amphibians, seven of them of the genus Telmatobius between Bolivia and Peru. Quite an achievement, although the uneasiness continues to prevail when he recalls it: "Discovering new species for science and seeing them disappear before your very eyes is, for a naturalist, something desolate and depressing. What is happening with the amphibians and those who study them is comparable to traveling to the Cretaceous and studying dinosaurs just before the fall of the famous meteorite that killed them. "

Where does chytridiomycosis come from and where does it go?

The terrarophilia and the consequent trafficking of amphibians as pets, the use and transfer of specimens between laboratories, the trade to extract supposedly curative substances or to determine the pregnancy of women … The causes that are adduced as propagators of a disease that attacks especially are varied. a sensitive and important organ for amphibians such as their skin, and whose oldest record dates back to 1863. It has been the extension of world trade (the fungus is able to survive even outside the host amphibian, in a plant, in a bird …) which has led to the extension of chytridiomycosis.

"At the beginning of the nineties the Asian pathogenic strain entered Bolivia, a new variant that attacked species of frogs that had not been affected previously. Another example is the Asian tritons that were taken to the center of Europe and infected our endemic species with another species of chytridium, "says Ignacio de la Riva. These variations and mutations make it very difficult to fight against fungus and disease. Specific actions have been taken, drying pools, capturing individuals to treat them with fungicides or keeping them at a temperature at which the fungus does not survive, but none has managed to stop the decline at the population level.

All researchers also conclude that there are other impacts that contribute, such as climate change, which makes amphibians even more sensitive and prone to being attacked by the fungus. And of course other threats are cited: habitat destruction, water contamination and introduction of exotic fish and invaders that devour their eggs and larvae.

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