Frogs Through Time, Modern Portraits of Species Discovered Two Centuries Ago

Two hundred years ago a couple of young explorers set sail on what was to become one of the greatest scientific expeditions of all time. In 1817 Johann Baptist Ritter von Spix and Carl Friedrich Philipp von Martius joined a naval excursion to Brazil and were given a humongous task—documenting the biodiversity and culture of that poorly known and largely exotic country. What they found during their three-year field trip would help lay the foundations of biodiversity research in South America. The importance of their scientific legacy is undeniable—hundreds of species discovered and detailed accounts on Brazilian indigenous cultures and habitats that have either vanished or been extensively altered through time.

Frontispiece illustration of the book “Travels in Brazil in the years of 1817-1820” by Spix and Martius. The book contains vivid accounts of the trip and the discoveries made by the two young scientists during their expedition.

Here, I celebrate the 200th anniversary of the Spix and Martius expedition with a small collection of frog portraits. Why frogs? As a National Geographic Explorer, I document frog biodiversity around the world. Over the past decade I visited many of the places where Spix and Martius collected their material—luckily, I encountered and photographed many of the frog species collected by the two young scientists.

Spix’s Snouted Treefrog (Scinax nebulosus), one of many frogs discovered and described by Johann Baptist Ritter von Spix during his travels through unexplored Brazilian forests in the 19th century. Photo by Pedro Peloso.

Travels in Brazil, in the years 1817-1820

The trip to Brazil was made possible by an unusual chain of events. Maximilian Joseph—the king of Bavaria and a generous patron of the sciences—had plans to research South American culture and biodiversity as early as 1815. For a long time, however, these plans were postponed. That changed when an important wedding revived the majesty’s dreams of studying the untamed American continent: the archduchess of Austria, Maria Leopoldina, was to be married to the prince of Portugal, Dom Pedro de Alcantara, who lived in Brazil at the time—the Portuguese crown was living in exile since they fled Portugal during the Napoleonic wars. The marriage strengthened the relationship between Bavarian countries and the Portuguese crown, and King Joseph saw this as a unique opportunity to revive his dreams to send a scientific party to Brazil. He then commissioned Spix and Martius to join a large party of officials and guests that would travel to Brazil in anticipation of the arrival of the bride.

The party left Munich on the 6th of February 1817, and after months in rough seas they arrived in Rio de Janeiro in the serene and bright morning of July 14th. Spix and Martius spent a couple of months in Rio fulfilling bureaucratic duties with the crown before venturing into undocumented Brazilian landscapes. Spix and Martius wondered through the megadiverse Atlantic Rainforest and the dry habitats of the Caatinga before finally reaching the Amazon basin, in the last and longer part of the trip. Beautiful accounts of the trip are detailed by Spix and Martius in their book “Travels in Brazil, in the years 1817-1820”, which they wrote as a travel report to King Joseph in 1824.

Rock River Frog (Thoropa miliaris). This species was probably discovered at Spix’s and Martius’s first stop, in Rio de Janeiro, Brazil. We now know that females of this species lay their eggs not on water, but on humid rocks, where tadpoles complete their entire development. Spix’s drawing, upper left, obtained through the Biodiversity Heritage Library. All photos by Pedro Peloso.

Scientific legacy of Spix and Martius

Wherever they went, Spix and Martius collected material and took detailed notes on the fauna, flora and local culture. They collected physical specimens of hundreds of species of plants and animals, which served as basis for the formal description of many new species upon their return to Europe. Unfortunately, a large part of their collection is now lost. The forests they visited transformed into cities, and some indigenous groups they so elegantly characterized are either extinct or their culture vastly changed. A lot of what they saw during those long three years can now only be seen through their written memories and illustrations.

The zoological part of the work was commissioned to Spix—Martius was assigned to report on plants. A large portion of Spix’s zoological material was deposited in Natural History Museum of Munich (Zoologische Staatssammlung München), although some specimens ended up in other European institutions as well. Part of this material still exists and is extremely valuable for taxonomy (the science of classification of all living organisms), whereas a big chunk of the collections was unfortunately lost over time—most of them destroyed from bombs dropped by the Allies over Nazi Germany during World War II.

Map Tree Frog (Boana geographica). Spix originally named two different varieties of this species, but genetic studies suggest that many more actually exist. The original specimens used in the descriptions were lost during WWII. This now poses a major challenge to the taxonomy of these frogs. Spix’s drawing, upper left, obtained through the Biodiversity Heritage Library. All photos by Pedro Peloso.

The humongous task—to describe the fauna of a mega diverse country—and complications of illnesses acquired in the Tropics, prevented Spix from completing his writings. He did, nonetheless, write several books about the Brazilian fauna, including volumes on Monkeys and Bats, Birds, Turtles and Frogs, and on Caimans and Lizards. Additional monographs, dedicated to other animal groups, were completed by trusted colleagues—largely based on his notes and specimens.

Spix’s impact on the study of the Brazilian herpetofauna (amphibians and reptiles) is undeniable. Together with the work of fellow German explorer, Prince Alexander Philipp Maximilian zu Wied-Neuwied, his writings formed the basis for the study of the country’s herpetofauna for many years—and in some ways, continue to do so. Not all species illustrated by Spix were new to science—some were already known before him, by Linnaeus (1758), Wied-Neuwied (1820-1825), or others. Moreover, he also committed a few mistakes, such as naming newborn, juvenile and adult Green Iguanas as different species. Nonetheless, his depictions were fairly detailed, despite rarely extending more than a page. Most descriptions are accompanied by at least one illustration, and although some of the illustrated renderings of species may be scientifically inaccurate, their artistic value is immensurable.

Common Lesser Toad (Rhinella granulosa). The species in common across drier areas of South America and was probably named in reference to its warty skin (many granules). Spix’s drawing, upper left, obtained through the Biodiversity Heritage Library. All photos by Pedro Peloso.

Modern exploration, and a new perspective onto Spix’s work

Much has advanced in our understanding of frog diversity. Since Spix left South America on his way back to Europe, hundreds of new species have been named. Moreover, modern genetic analyses have shown that some of the frog species recognized by Spix have large levels of variation in their DNA. Such cases suggest that a species described decades ago may actually represent more than one species. In order to properly recognize these species that have unique DNA, we need to know exactly which of them were represented in century-old descriptions, such as those provided by Spix. This is where things get tricky. Most of the old descriptions are not very accurate, according to today’s standards. As a result, present-day scientists cannot always be sure of which species—as indicated by unique DNA lineages—these earlier explorers were referring to. These uncertainties open the doors to new avenues for exploration—retracing the steps of early naturalists in new scientific expeditions. In such cases, it is key to sample as close as possible to the site where the original frogs were collected. I have embarked in such expeditions, sometimes with great success. As an explorer, nothing compares to the excitement of finding a species that someone discovered at that same place, two centuries ago!

Spix’s Green Treefrog (Boana cinerascens) was originally discovered in Tefé. Genetic studies suggest that many different species of green treefrogs existin order to know exactly which of these species was named by Spix, I recently traveled to Tefé, Amazonas, where the species was originally discovered. Spix’s Plate, upper left, obtained through the Biodiversity Heritage Library. All photos by Pedro Peloso.

Pedro Peloso is a National Geographic Explorer who dwells through Tropical forests around the World in search of unknown, rare and endangered species. He has a PhD in Comparative Biology from the American Museum of Natural History and specialized in the biology and taxonomy of amphibians and reptiles. Pedro discovered and named many species of frogs and lizards—most from Amazonia.

Follow Pedro Peloso on Facebook and Instagram for updates on his research and lots of wildlife photos.

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Pedro Peloso is a National Geographic Explorer who dwells through Tropical forests around the World in search of unknown, rare and endangered species. He has a PhD in Comparative Biology from the American Museum of Natural History and specialized in the biology and taxonomy of amphibians and reptiles. Pedro discovered and named many species of frogs and lizards—most from Amazonia. Follow Pedro Peloso on Facebook and Instagram for updates on his research and lots of wildlife photos.