Discovery of Gitchak Nakana: A Hidden Gem in Assam's Aquifers

In a remarkable breakthrough for biodiversity research, scientists have unveiled Gitchak nakana, a previously unknown miniature loach species thriving in the dark depths of Northeast India's groundwater aquifers. This blind, translucent fish, measuring just over 2 centimeters, was found in a traditional dug-out well in Goalpara district, Assam, marking the first documented aquifer-dwelling—or phreatobitic—fish from the region. The discovery highlights the untapped subterranean world beneath the Shillong Plateau's foothills, close to the Brahmaputra Valley, and underscores the role of serendipitous finds in advancing ichthyology.

Phreatobitic species like Gitchak nakana inhabit aquifers—porous underground layers saturated with water that serve as vital freshwater reservoirs. Unlike cave-dwelling fish, which are more commonly studied, aquifer species are rarely encountered, comprising less than 10% of the over 300 known subterranean fishes globally. This find not only expands our understanding of loach evolution but also spotlights Northeast India's rich, yet vulnerable, groundwater ecosystems.

Physical Characteristics and Troglomorphic Adaptations

Gitchak nakana belongs to the Cobitidae family, commonly known as loaches, which are bottom-dwelling freshwater fishes characterized by their elongated bodies and barbels for sensing prey in murky waters. This new species exhibits classic troglomorphies—adaptations to perpetual darkness and isolation—including the complete absence of functional eyes, lack of body pigmentation for a ghostly translucent appearance, and extreme miniaturization with a maximum standard length (SL) of 20.8 mm.

Its most striking feature is the total lack of a skull roof, leaving the brain protected only by a thin layer of skin—a rarity seen in just three other miniaturized cypriniform fishes. Elongated barbels (up to two-thirds of head length) aid navigation, while the body lacks scales and a lateral line canal. In life, it displays a vivid red hue from prominent blood vessels, earning its genus name 'Gitchak' from the Garo word for red. The species name 'nakana' combines Garo terms 'na·tok' (fish) and 'kana' (blind), honoring the local indigenous community.

Reproductive traits include few large eggs (5-8 per female, 1-1.5 mm), suggesting a strategy suited to scarce subterranean food resources. Micro-CT scans revealed 48-49 vertebrae and unique extensions of the swimbladder capsule to the seventh vertebra, further distinguishing it from relatives like Pangio and Lepidocephalichthys.

The Serendipitous Journey from Well to World Recognition

The story began in March 2021 when PhD scholars from Assam Don Bosco University collected 13 specimens during three visits to the same well in an undisclosed village in Goalpara. Local collector Leminard K. Marak played a crucial role in securing the samples. Initially preserved in ethanol and formaldehyde, the specimens were analyzed using advanced techniques: µCT scanning for 3D skeletal imaging at Germany's Senckenberg collections and molecular sequencing at the University of Bern and Kerala University of Fisheries and Ocean Studies (KUFOS).

Genetic analysis of cytochrome b, RAG1, and COI genes placed Gitchak as a distinct lineage within Cobitidae, diverging from its closest relatives 21-45 million years ago. This multidisciplinary approach, blending morphology, osteology, and phylogenetics, culminated in the species' formal description published on February 26, 2026, in Scientific Reports, a Nature Portfolio journal.Read the full paper

Indian Universities Driving the Research

Indian researchers were pivotal, with Wimarithy K. Marak and Kangjam Velentina from Assam Don Bosco University's School of Life Sciences leading collections and fieldwork. Yumnam Lokeshwor from Dhanamanjuri University, Imphal, Manipur, confirmed early identifications, while Rajeev Raghavan from KUFOS contributed molecular expertise. These institutions exemplify how Northeast Indian universities foster cutting-edge biodiversity research amid the region's status as an Indo-Burma biodiversity hotspot.

Such collaborations highlight opportunities in research jobs and faculty positions at these universities, where studies on endemic fishes advance global ichthyology. For aspiring researchers, programs at Assam Don Bosco and KUFOS offer hands-on training in aquatic ecology, aligning with India's National Mission on Biodiversity.

Ecological Niche and Habitat Insights

Gitchak nakana inhabits lateritic aquifers—porous rock formations typical of the Shillong Plateau—accessed via shallow dug wells (3-5 meters deep). These aquifers, formed in Middle-Late Pleistocene alluvial deposits, provide stable, oxygen-poor environments isolated from surface waters. The well's ecosystem likely includes microscopic prey detected via enhanced sensory barbels and chemoreception.

Unlike nearby cave species like the giant blind mahseer Neolissochilus pnar or nemacheilid loaches Schistura spp., Gitchak represents a distinct phreatic lineage, suggesting aquifers harbor unique evolutionary histories. This underscores Northeast India's dual subterranean realms: karst caves and laterite aquifers.

Biodiversity Hotspot Status of Northeast India

Northeast India boasts over 800 fish species, with loaches comprising a significant portion due to the Brahmaputra's diverse habitats. The Indo-Burma region ranks among the world's top 35 biodiversity hotspots, yet subterranean fauna remains understudied. Gitchak nakana's discovery adds to 20+ endemic subterranean fishes in India, mostly from the Western Ghats, revealing NE India's parallel hidden diversity.

Universities like Tezpur University and Gauhati University complement this work through wetland and riverine studies, training the next generation of conservation biologists.

Conservation Challenges Facing Aquifer Ecosystems

Groundwater overexploitation, urbanization, and agricultural runoff threaten these fragile habitats. In Assam, tube wells and jhum cultivation exacerbate aquifer depletion, risking endemic species like Gitchak. Past incidents, such as the aquarium trade exploitation of Meghalaya's cave mahseer, highlight vulnerabilities—exact locality is withheld to prevent similar fates.NENow on conservation

• Rapid groundwater drawdown reduces habitat connectivity.
• Pollution from pesticides infiltrates aquifers.
• Climate change alters recharge patterns.
• Lack of surveys misses cryptic species.

Stakeholders urge integrating aquifer protection into Assam's water policy, with universities advocating community-led monitoring.

Research Methodologies and Technological Advances

The study employed non-destructive µCT scanning (voxel sizes 2.6-8.8 μm) to reveal unprecedented skeletal details without specimen damage. Molecular phylogenetics using BEAST divergence dating provided evolutionary timelines, while comparisons with 178 cobitids confirmed novelty. This gold-standard approach sets a benchmark for future NE India surveys.

For students eyeing academic careers, mastering such tools opens doors in fisheries research.

Photo by Uday Kiran on Unsplash

Future Prospects and Calls to Action

Prospects include aquifer-wide surveys using eDNA and remote sensing to uncover more phreatobites. Collaborative grants via India's ICAR and DST could fund university-led initiatives. Protecting sites like Goalpara's wells requires policy: regulate deep borewells, promote rainwater harvesting, and educate locals on biodiversity value.

Explore research assistant jobs or university jobs in India's aquatic sciences to contribute. Institutions like Assam Don Bosco University seek talent for expanding biodiversity programs.