New Species Of Blind Swamp Eel Discovered

New Species Of Blind Swamp Eel Discovered

Researchers stumbled upon a new species of swamp eel—blind as a bat and slick as a snake.

The fish was uncovered in damp soil of the Indian rainforest by researchers searching for an entirely different animal.

“We were digging all day every day for caecilians in the Khasi Hills of Meghalaya, in the north-east of India, when I chanced upon this fish,” Natural History Museum (NHM) of London researcher Rachunliu Kamei said in a statement. “This is the only specimen of the species, as we couldn’t find any more.”

The so-called Monopterus rongsaw—so distinct, this individual was enough to convince researchers they discovered a new species—is described in the journal Ichthyological Exploration of Freshwaters.

Swamp eels are a family of freshwater fish, typically found in the tropics and subtropics. Most are able to breathe air and typically live in marshes, ponds, and damp places, sometimes burying themselves in mud if their water source dries up.

Some, however, have evolved far more specialized, subterranean lifestyles, according to the Museum. The new species, for instance, was detected some 55 yards from the nearest stream.

Which means very little is known about these slithery critters, as folks who study fish tend to be looking, well, in water.

CT scans of the fish’s head reveal its formidable-looking skull
CT scans of the fish’s head reveal its formidable-looking skull (via Ralf Britz/Natural History Museum)

“More swamp eels have been collected by my herpetologist friends than I have ever collected with my fishing net,” according to Ralf Britz, fish researcher at the NHM and co-author of a paper with Kamei.

Herpetology is the study of amphibians and reptiles.

The M. rongsaw‘s underground way of life has forced certain adaptations, including being blind.

“We suspect that the eyes just never really develop,” Britz explained. “We can’t say that for certain for this particular species as we don’t have early life stages, but that is something I would expect.”

Their “vivid pink” coloring, as reported by the Museum, is also a result of their sunken existence: The fish have simply lost all pigmentation. Add to that an increased number of blood vessels (allowing for oxygen exchange), and you get a fuschia-tinted, worm-like specimen with disturbingly sharp teeth.

One thing these little serpents have in common with their swamp eel brethren is a lack of gill filaments: Oxygen is absorbed through the lining of the mouth and pharynx, which acts as a “lung.”

And though full-grown swamp eels have virtually no fins, the larvae are born with large pectoral fins, used to fan water over their bodies before their adult breathing apparatus develops.

It remains unclear whether these appendages simply fall off, or are reabsorbed by the fish.

The region in which the eel was found is covered in rich rainforest
The region in which the eel was found is covered in rich rainforest (via Rachunliu Kamei/Natural History Museum)

There are only 25 known species of swamp eel, distributed across South and Central America, West Africa, India, and further east. The newest eel was found in a remote part of India, traditionally regarded as a transitional zone between the Himalayas and Indo-Burma hotspots.

“But this has turned out not to be true,” Kamei, a Marie Curie Fellow at the Museum, said. “Rather than being a transitional zone, it seems to have its own set of species with deep evolutionary roots. It’s a really fascinating area, but greatly undersampled.”

It is now recognized by the International Union for the Conservation of Nature as the Eastern Himalaya Biodiversity Hotspot. Scientists hope further studies in this poorly documented region will reveal “a host of hidden diversity to keep the new species of blind swamp eel company.”