New species of fish that evolved in absolute darkness

16 Feb. () –

Genetic studies have revealed a new species of catfish Horagalanis, a tiny freshwater fish only 3 centimeters in lengthwhich lives in lightless aquifers in Kerala, South India.

Life in aquifers is characterized by total darkness, low concentration of nutrients, dissolved carbon and oxygen, hydrographic isolation, and limited dispersal capacity.

“Currently, 289 species of fish from subterranean aquatic habitats are known worldwide, of which less than 10% live in aquifers,” he explains. it’s a statement Dr. Ralf Britz, from the Dresden Senckenberg Natural History Collections and member of the team that discovered the new fish.

“To gain insight into this largely unknown biotope, we conducted a six-year study of water-bearing lateritic rock layers and their fascinating fish fauna in the southern Indian state of Kerala.”

Specifically, the researchers focused on the catfish genus Horaglanis. These fish live exclusively in aquifers, are very small, blind and lack pigment. “There are very few documented cases of these species: as a rule, these elusive minnows only surface when a home well is being dug or cleanedBritz adds.

So the Dresden biologist and his Indian colleagues, led by Dr. Rajeev Raghavan of Kochi University and Dr. Neelesh Dahanukar of Delhi’s Shiv Nadar University, also enlisted the help of local citizen scientists. . Over the course of six years, they conducted a series of workshops, focus groups, and informal conversations with communities in various locations, including the type localities of the three Horaglanis species known to date.

“Local people are often the only ones who get to see such well-hidden species. They can therefore play an important role in improving our scientific understanding of this unusual fauna. We inform local villagers about the importance of the species of underground fish and their conservation needs and we asked them to share with us information, photos or videos when they found and/or collected these species.”

The researchers complemented this citizen science approach with selective collection activities in pits and aboveground storage tanks, with trawl nets in shallow wetlands, water channels, home gardens and plantations, and with the use of baited traps in dug pits on farms, in ponds, and in caves.

“This allowed us to generate data sets with a total of 47 new site detections and 65 new genetic sequences. These demonstrate, among other things, that the Horaglanis are endemic to the part of Kerala state lying south of the Palghat gap. -the mountain pass also seems to represent a biogeographical barrier to the underground world-“, explains Britz.

“The genus is characterized by a high level of genetic diversity that has evolved over millions of years, although the appearance of the fish has changed very little”.

WITHOUT EYES AND WITH A RED BODY

In addition, the team managed to identify a new species: Horaglanis populi is a catfish that measures no more than 32 millimeters, lacks eyes and has a blood-red body, and is genetically distinct from the three Horaglanis species known so far.

“The specific name populi, a genitive of the Latin noun ‘people’, honors the invaluable contribution of the interested public in Kerala, who helped document the biodiversity of these subterranean fish, including the discovery of the new species“, says Britz.

“Our Horaglanis project is an excellent example of how public participation can greatly increase our knowledge of rarely collected organisms living in relatively inaccessible habitats. The local population enlarges the ‘eyes and ears’ of researchers by several orders of magnitude.”

Species with small ranges – such as Horaglanis populi – are considered to be at high risk of extinction, especially if they live in subterranean habitats. According to the study, fish in the study area enjoy little or no protection under local or regional laws, and their habitats are embedded in densely populated landscapes. Both the extraction of groundwater and the mining of lateritic rock layers threaten the animals.

“To ensure the survival of Kerala’s enigmatic subterranean catfish, a planning and implementation approach is needed that involves a wide range of stakeholders. This must also include the local population, whose support was instrumental in moving our research to the its current state,” says Britz.