<p><em>A rare species of catfish, has been found in aquifers in Kerala, opening a window to the rich biodiversity that exists even in deep and dark underground subterranean environments where unique organisms survive by adapting to the harsh surroundings informs this paper titled '<a href="https://vertebrate-zoology.arphahub.com/article/98367/">Evolution in the dark: Unexpected genetic diversity and morphological stasis in the blind, aquifer-dwelling catfish Horaglanis</a>' published in <a href="https://vertebrate-zoology.arphahub.com/">Vertebrate Zoology</a>.</em></p>
This was a unique effort made by scientists to involve citizens in identifying these rare species as a part of the ‘citizen science’ campaign that helped raise awareness on the subterranean fauna of southern India, and led to increased reports on the occurrence of these rare and interesting fish species. This also led to more specimens becoming available for research.
While a lot is known about the biodiversity and the range of interesting organisms –vertebrates as well as invertebrates found in freshwater ecosystems such as streams, lakes, rivers, ponds, what kind of life exists in the water beneath the surface of the earth still remains a mystery.
<p><em>As much as 97 percent of the earth’s freshwater resources other than the polar ice caps are stored as groundwater. Groundwater is stored in aquifers - bodies of rocks that are capable of storing large quantities of water in pores and open spaces that are large enough and interconnected to transmit water. And aquifers can go very deep, even as deep as 30,000 feet.</em></p>
Groundwater from the aquifers can be accessed by pumping or drawing out water through dugwells, borewells, tubewells and used for drinking and irrigation. Occasionally, this water can bring along with it wonders of the natural world that include rare varieties of animals living inside the deep hidden waters in caves or subterranean environments, unknown to the world outside.
Subterranean aquatic habitats often harbour unique type of fish such as bony fish, with 289 species being currently known to dwell in subterranean aquatic habitats in every continent except Antarctica. These include cave-adapted species or lineages of ‘living fossils’ . These unusual fish species have been aptly called the ‘wrecks of ancient life’ and ‘ghosts in the water’. While subterranean habitats are known to harbour extraordinary varieties of such animals, many of these remain under studied and unknown because of their inaccessibility.
Chance encounters with these subterranean animals often happen through dug wells and local communities are often the first or sometimes the only people to encounter these species and can thus play a significant role in improving scientific knowledge on these rare and mysterious deep dwelling animals in environments that are dark, have reduced concentrations of nutrients, carbon and dissolved oxygen, and free space.
The lateritic landscape in the state of Kerala in India is a global hotspot for subterranean fish and harbours a rare and rich variety of subterranean fish with it presently including 10 endemic species in five genera (Aenigmachanna, Horaglanis, Kryptoglanis, Pangio and Rakthamichthys) and two monotypic families (Aenigmachannidae and Kryptoglanidae). Some of these fish exhibit unusual morphological characters such as absence of eyes and body pigments, absence of dorsal or pelvic-fins or even both fins.
Horaglanis, is a type of catfish that is blind, pigmentless and of blood-red coloration, is of a tiny size (< 35mm) and occurs in unique habitats (lateritic aquifers), but is rarely found appearing only occasionally in dug-out wells. Though three species of this catfish are currently known, two continue to be poorly described and there is no information on the differences between the three species.
The paper discusses the findings of a six-year exploratory and citizen science-backed survey across the lateritic landscape of Kerala that resulted in extensive information on Horaglanis. Samples were obtained from dug-out wells, borewells, natural wetlands adjacent to lateritic zones, home-gardens and plantations, as well as lateritic caves.
<p><em>Community involvement in the study was encouraged through a series of workshops, focus-group discussions and informal interactions. Local villagers were informed of the importance of the species and their conservation needs, and they were asked to share information, photographs or videos if the species were encountered and/or collected.</em></p>
This approach was complemented by targeted collection efforts by researchers through draining of wells and overhead storage tanks, the use of scoop nets in shallow wetlands and in water channels in home gardens and plantations, as well as the use of baited traps in dug-out wells in homesteads, ponds and caves.
Horaglanis have no legislative protection till now because of lack of adequate information although their habitats continue to be invaded more and more with human populations and human activities such as high extraction of groundwater for both household and agricultural purposes and mining of laterite soil. . Also the fish are found in many areas near the coast which increases the risk of seawater intrusion into the aquifer systems thus killing the fish.
The paper argues that it is important to conserve these rare and beautiful catfish and ensuring the security of these fish in the lateritic aquifers of Kerala will require landscape-level planning and implementation involving a variety of stakeholders including local communities who can play an important part in building knowledge and protecting these enigmatic catfish.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0),
Image Source: By Rajeev Raghavan, Remya L. Sundar, C.P. Arjun, Ralf Britz, Neelesh Dahanukar - Evolution in the dark: Unexpected genetic diversity and morphological stasis in the blind, aquifer-dwelling catfish Horaglanis, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=128832101.