Daniel Kim/© AMNH
Fish that live in the Congo River Basin navigate one of the world’s most demanding freshwater environments. The basin’s powerful currents, seasonal flooding, and maze of deep channels create challenges for finding food, avoiding predators, and navigating murky waters where visibility is often extremely limited.
As a result, many Congo River fish species have evolved specialized adaptations. These include streamlined bodies, enlarged pectoral fins, or suction-like structures that help them cling to rocks and avoid being swept away; the ability to use electric fields to navigate, locate prey, and communicate in poor visibility; and camouflage to blend in with river bottoms or vegetation.
Most recently, scientists have discovered that a particular group of Congo Basin catfish might even “sniff” underwater, which could be advantageous in the low-visibility habitats of the turbulent river.
The researchers, Axelrod Research Curator Emeritus Melanie Stiassny and Allison Bronson, an alumna of the Museum’s Richard Gilder Graduate School, detailed a unique nasal structure that may allow these catfish (Parauchenoglanis punctatus) to actively draw water and scent molecules through their noses.
Researchers visualized the species’ bizarre nasal anatomy using traditional dissection, scanning electron microscopy, histological sectioning, and high-resolution CT scanning, working with specimens that had been collected by a team of Congolese and American scientists on a series of expeditions and brought back to the Museum for study.
They found that a thin membrane suspends the fishes’ sensory tissue within the nasal cavity. Unlike most fishes, which rely on cilia to move water across smell receptors like a conveyor belt, this anatomy may allow the catfishes to actively pull water in or “sniff.”
The mechanism is unlike anything described before in fishes. The study, which appeared in
“In most fishes, tiny cilia beat within the nose to generate a water current that brings scents toward the sensory tissue,” said Bronson, a professor at California State Polytechnic University, Humboldt. “But, instead, these fish can sniff water and scent molecules into the nose, which may heighten their odorant-sensing abilities.”