BIODIVERSITY/ICHTHYOLOGY - Fish collected by Alfred Russel Wallace 160 years ago is finally described

Wallace's drawing of Crenicichla monicae collected in the Upper Rio Negro 
in Amazonia over 160 years ago (image: Alfred Russell Wallace)

PETER MOON

An expedition to the Upper Rio Negro in the Brazilian Amazon led by Alfred Russel Wallace (1823-1913), co-discoverer of the mechanism of natural selection with Charles Darwin, continues to deliver scientific dividends even today, 160 years after the expedition took place.

Two biologists, one Swedish and the other Brazilian, have described a fish collected by Wallace, basing their work on notes and drawings left by the great British naturalist. The specimens that he collected in Brazil were lost long ago when he was shipwrecked on his voyage home.

The new species is Crenicichla monicae, a pike cichlid approximately 30 cm long and with several dark spots on its side and fins. It belongs to the same family as the peacock bass (Cichla spp), a group that includes some of the largest and best-known Brazilian freshwater fish. To describe it, ichthyologists Sven O. Kullander from the Swedish Natural History Museum in Stockholm and Henrique Varella from the University of São Paulo’s Zoology Museum had to analyze the only three known specimens of the fish, which were collected by a Swedish expedition in 1923.

The paper describing their study, is noteworthy as a contribution to both biology and the history of science. It was published in the scientific journal Copeia.

On August 31, 1850, Wallace left Manaus by canoe for the Upper Rio Negro, traveling 900 km to where this mighty tributary of the Amazon is joined by the Uaupés. His goal was to draw and describe as much of the flora and fauna as he could, but he was particularly interested in studying the main fish species. He hoped to sell a large collection of specimens to London’s Natural History Museum on his return home.

Wallace could not count on family wealth, unlike Darwin, who could afford to devote his entire life to research. Wallace needed to earn a living and finance his dream of traveling around the world to study natural history. He spent almost two years in the Upper Rio Negro, a region that even today is isolated, inhospitable, and little explored. He caught malaria there and almost died.

In June 1852, he returned to Manaus. He was soon on his way to England via Belém, the capital of Pará State. He loaded his huge collection of living and preserved specimens onto the brig Helen, and they left on July 12. After 26 days, the brig caught fire in the mid-Atlantic. The passengers and crew were forced to abandon ship. Wallace was only able to save his papers, including diaries and sketches of fish that he had collected on the Negro. Everyone drifted in an open boat for ten days before being picked up by a passing ship from Cuba.

Wallace’s great Amazon adventure had ended tragically. His collection was lost, except for his drawings, which he gave to the Natural History Museum in London.

The story of how the new species of cichlid was rediscovered and described is a saga lasting more than a century and involving several protagonists. The plot begins in 1889, with the publication of Wallace’s narrative of his travels in Amazonia. It then jumps to the years 1923-1925, when a Swedish expedition to the Amazon collected the only three known specimens of C. monicae.

The material was stored undescribed for three decades in the Swedish Natural History Museum. In the 1950s, part of the collection was loaned to Otto Schindler, the first post-war curator of ichthyology at the Bavarian State Zoology Collection (ZSM) in Munich, Germany. The biological specimens collected by Spix and Martius in Brazil between 1817 and 1821 are housed at ZSM.

Schindler was busy restarting ZSM’s collections from scratch after the museum’s total destruction by Allied bombing in 1944. The fish specimens on loan from Sweden included two adult pike cichlids and one fry. According to his notes, Schindler realized that they must be a new species not yet described because of the coloring and patterns, and so they remained. With Schindler’s death in 1959, the location of these specimens was forgotten. They sat gathering dust in a cabinet at ZSM for the next 30 years.

While on a visit to Munich in the 1990s, Sven Kullander, curator of ichthyology at the Swedish museum, found the lost collection of fish specimens from the Negro that had been put together by his fellow countrymen in the 1920s. Like Schindler before him, Kullander realized that the three specimens represented a new species of pike cichlid. However, he was reluctant to describe it because the material had faded badly and he could see only the dark spots that are characteristic of the species.

Kullander put off describing the species in hopes of finding specimens in a better state of conservation. “We found no other exemplars in any European, American or Brazilian collection,” Henrique Varella said. “Those three individuals are the only ones anyone has heard of.”

Sketches rescued

Enter Wallace and the rescue of his sketches. In 2002, zoologist Mônica de Toledo-Piza Ragazzo from the University of São Paulo’s Bioscience Institute (IB-USP) collected the drawings conserved in London and published them in a book entitled Peixes do Rio Negro (EDUSP).

The book has 212 illustrations describing 180 species. This was the missing link. In the absence of new specimens, the description of the three specimens in Munich could be based on the drawings left by Wallace. “We noted that drawing number 46 had the characteristic spots, which were very similar to those of the pike cichlid specimens,” Varella said.

Here is how Wallace describes specimen 46: “Length 12-15 in. Color pale red. A dull red band from the point of the ventral fins to the anal [fin]. Eye orange red – nostrils single near the lips – scales fine smooth regular – teeth in a band file-like in both jaws – tongue large free… Pectoral and ventral fins pale.” Wallace collected it in Nossa Senhora da Guia, an island in the Upper Rio Negro, downstream of its confluence with Rio Içana.

The new species was named Crenicichla monicae as a tribute to Professor Mônica Toledo-Piza Raggazzo, “for her efforts in retrieving Wallace’s drawings,” Varella said.

The cichlids are one of the largest freshwater fish families, with some 1,700 species worldwide, 550 of them in South America. Cichlids vary considerably in size, ranging from a few centimeters in the case of Geophagus brasiliensis, the pearl cichlid, to 1 m in the case of the peacock bass (Cichla spp). The total number of cichlid species is believed to exceed 2,000.

“Many of Wallace’s drawings still haven’t been identified,” Varella said. “That could be due to inaccuracies or perhaps they’re new species. So it’s always important to look back at the oldest studies when you’re doing any kind of taxonomic analysis. They may contain valuable information.” Who knows? Those illustrations may one day reveal more unknown species.

And what about Wallace? What happened to him after surviving the shipwreck in 1852? 

Feeling wretched about the loss of his collection and completely broke, he struggled against hardships until he managed to travel in 1854 to what was then called the Malay Archipelago, which included what is now Indonesia, Borneo, Singapore and Malaysia. Having explored the biodiversity of Amazonia, with its various microbiomes separated by the barriers formed by enormous rivers, Wallace now met a different biodiversity spread over the geography of thousands of islands. This was where, in 1858, in the throes of delirium caused by the attack of malaria that he contracted in the Amazon, he said that he first glimpsed the principles of evolution by natural selection. The rest is history.

Wallace outlined his theory in a letter to none other than Charles Darwin, asking his opinion. On receiving the letter, Darwin was alarmed: he risked losing priority in announcing the theory on which he had been working for over 20 years. Wallace’s essay was presented to the Linnean Society of London on July 1, 1858, along with excerpts from unpublished writings by Darwin to establish his priority.

In 1859, Darwin published The Origin of Species and won the laurels of science and history. Wallace remained a secondary figure until his death, outshone by Darwin’s glory. The fame that was Wallace’s by right of being the co-discoverer of natural selection was not to solidify until the final decades of the twentieth century.

The article by Varella and Kullander, “Wallace’s Pike Cichlid Gets a Name after 160 Years: A New Species of Cichlid Fish (Teleostei: Cichlidae) from the Upper Rio Negro in Brazil,” published in Copeia (doi: http://dx.doi.org/10.1643/CI-14-169), can be read atwww.bioone.org/doi/abs/10.1643/CI-14-169.

Originally published at Agência Fapesp