An international team of researchers has made an exciting discovery in the southern Indian state of Kerala: a new species of catfish. The team, comprising German and Indian scientists, found the tiny Horaglanis populi, which measures just 32 millimeters, lacks eyes, and has a blood-red body, living in local aquifers without light.

The research, which was published in the journal Vertebrate Zoology, used a citizen science approach to gather information on the distribution, genetics, and evolutionary history of the genus Horaglanis of catfish, a diverse group of ray-finned fish.

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Ralf Britz of the Senckenberg Natural History Collections, who led the study, said: "Currently, 289 fish species are known from subterranean aquatic habitats worldwide -- less than 10 percent of them live in aquifers. In order to obtain information from this almost unknown biotope, we conducted a six-year study of water-bearing laterite rock layers and their fascinating fish fauna in the southern Indian state of Kerala."

Horaglanis fishes live exclusively in aquifers and are very small, blind, and lack pigments. Britz explained that "there are very few documented occurrences of these species -- as a rule, these elusive little fish only come to the surface when a domestic well is being dug or cleaned."

The researchers relied on the cooperation of local citizen scientists to conduct a series of workshops, focus group discussions, and informal conversations with communities at several sites, including the type localities of the three Horaglanis species known to date.

The team complemented this citizen science approach with targeted collection efforts in wells and above-ground storage tanks, with scoop nets in shallow wetlands, water channels, home gardens, and plantations, and with the use of baited traps in excavated wells on farmsteads, in ponds, and caves. This allowed them to generate data sets with a total of 47 new site detections and 65 new genetic sequences.

In addition to identifying the new species of catfish, the team's research revealed that Horaglanis are endemic to the part of Kerala state south of the Palghat Gap.

"The mountain pass apparently represents a biogeographical barrier for the subterranean world as well," Britz explained. "The genus is characterized by a high level of genetic diversity that has evolved over millions of years -- although the fishes' appearance has changed remarkably little."

Britz said that the discovery of the new species was due in part to the invaluable contributions of the interested public in Kerala who helped document the biodiversity of these subterranean fishes.

"Our Horaglanis project is an excellent example of how public involvement can greatly increase our knowledge of rarely collected organisms that live in relatively inaccessible habitats. Local people expand the researchers' 'eyes and ears' by several orders of magnitude," he added.

The discovery of Horaglanis populi underscores the importance of citizen science in expanding our understanding of the natural world. The findings of this study have significant implications for conservation efforts in Kerala and beyond, and they highlight the need for further research into the poorly understood subterranean aquatic habitats of the world.

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(Edited by : Soham Shetty)