One of the most surprising discoveries noted in the report was Danionella cerebrum, found in southern Myanmar. This tiny transparent fish—only slightly longer than a thumbnail—has been used in research by neuroscientists for years because it has an open brain cavity that lets researchers noninvasively observe how its neurons function. But the scientific community had thought the species was the visually similar Danionella translucida. It was only after a team of researchers studied the DNA sequences that they realized the fish represented an entirely new species, which split apart evolutionarily about 13 million years ago. D. cerebrum “helps us understand how miniature size, simplified anatomy and evolutionary novelties all coexist in a vertebrate organism,” says Ralf Britz, lead author of the paper describing the species in Scientific Reports an ichthyologist at the Senckenberg Natural History Collections in Dresden, Germany.
Another intriguing find in the Shoal report was the Mumbai blind eel (Rakthamichthys mumba), which evolved around 170 million years ago, close to the time when the region that is now India broke off from the supercontinent Gondwana. The eel has no eyes, fins or scales. And coincidentally, it was found at the bottom of a 40-foot well at a school for blind people in Mumbai. “When my collaborator Tejas Thackeray repeatedly told me that he found a blind eel in a school well, located near a busy railway station of Mumbai, I did not believe him until I saw the live specimens,” says Jayasimhan Praveenraj, a fisheries scientist at the Indian Council of Agricultural Research (ICAR)–Central Island Agricultural Research Institute, who co-authored the study in Aqua that described the eel. “It made me realize that we often ignore and underrate highly populated places for ichthyological exploratory studies. We now understand not to leave any stones unturned.”
That well was not the only unexpected place a new species turned up. A group of scientists spotted the Etowah bridled darter (Percina freemanorum) in the Etowah River system in the state of Georgia. The discovery shows that there is still much to be learned about life under the water’s surface, even in a well-studied country such as the U.S., the Shoal report says.
The cases of the newly discovered Parosphromenus juelinae and Parosphromenus kishii exemplify the plight of some of these species. These tiny, bright and glittering fishes live only in peat swamps in Southeast Asia. One of P. juelinae’s habitats was converted to a paddy field, and P. kishii’s habitat was made into an irrigation canal for a palm oil plantation. Researchers are calling for the urgent protection of these species because both qualify for critically endangered status on the International Union for Conservation of Nature’s Red List of Threatened Species.
With its report, Shoal aims to highlight the search for new species as a critical part of the effort to save threatened freshwater fish. “Descriptions of new species help identify locations with exceptionally high levels of diversity or endemism [when species are restricted to particular area],” says Harmony Patricio, Shoal’s conservation program manager and a co-author of the new report. They also “call attention to species that may have only just been discovered because they’re already headed down the road toward extinction or are naturally rare. This knowledge helps to prioritize sites and species where conservation action can be most effective or is most urgent, enabling conservationists to protect a greater number of threatened species and stem extinctions.”
