A chance discovery
The story of the Aenigmachanna snake-eel begins not in a laboratory, but in a paddy field in Kerala, India. After the region's severe floods in 2018, a local man discovered a strange, eel-like fish and posted photos of it on social media. These images caught the attention of researchers at the Kerala University of Fisheries and Ocean Studies, who recognized it as something completely new to science.
The fish, Aenigmachanna gollum, had been living undetected in the subterranean aquifers beneath the Western Ghats. The floodwaters had washed these hidden animals out of their usual habitat and into the open. The discovery revealed a hidden ecosystem of unique subterranean fauna. Kerala's aquifers are now known to harbor at least eleven unique subterranean fish species.
The fish has a long, slender body, a large mouth, and is typically a uniform cinnamon-brown color. It can reach a length of about 12.7 cm. Unlike many subterranean species, the fish has well-developed eyes and pigmentation. However, it possesses many characteristics adapted for life underground, including a very slender, eel-like body for navigating crevices, and it lacks pelvic fins entirely.
A living fossil from a lost supercontinent
Scientific analysis of Aenigmachanna gollum revealed something astounding. This fish is a new species and a member of an entirely new family, Aenigmachannidae, which scientists created to classify it. It is called a "living fossil" because it retains numerous primitive characteristics seen in ancient fish lineages.
Genetic and morphological studies show that the Aenigmachannidae lineage diverged from its closest living relatives, the Channidae (common snakeheads), as long as 109 to 120 million years ago. This separation corresponds with the breakup of the supercontinent Gondwana, when the Indian subcontinent began to drift away from Africa. This suggests Aenigmachanna is a Gondwanan lineage that survived the continental split and subsequent extinction events that wiped out the dinosaurs, likely by sheltering in its subterranean habitat.
Its unique anatomy distinguishes it sharply from surface-dwelling snakeheads. It has a reduced swim bladder, meaning it cannot maintain buoyancy in the water column. It also lacks the suprabranchial air-breathing organ that allows other snakeheads to breathe air. High-resolution CT scans confirmed these and other skeletal features are so different that they warranted the creation of a new family.