Anglerfish are some of the most fascinating creatures in the deep sea, known for their glowing lures and bizarre shapes.
A new study by researchers at Rice University reveals how these unusual fish have defied expectations to adapt and thrive in the harsh, dark depths of the ocean.
Published in Nature Ecology & Evolution, the study uncovers how anglerfish evolved in one of the toughest environments on Earth—the bathypelagic zone, which lies 3,300 to 13,000 feet below the ocean’s surface.
Led by biologist Kory Evans and former student Rose Faucher, the team used advanced genetic analysis and 3D imaging to trace the evolutionary journey of anglerfish.
They found that these deep-sea marvels started out as seafloor-dwelling creatures before moving into the open ocean, where they developed unique adaptations to survive in a resource-scarce, pitch-black environment.
The journey to the deep
Anglerfish (scientific group Lophiiformes) are famous for their bioluminescent lures, which dangle from their foreheads to attract prey in the dark waters.
But their evolutionary story goes far beyond this signature feature.
The study reveals that the ancestors of today’s deep-sea anglerfish, called ceratioids, once lived on the continental slope, near the seafloor. Over time, these fish transitioned to the open waters of the deep ocean, triggering rapid evolutionary changes.
To cope with the challenges of their new environment, ceratioids developed larger jaws, smaller eyes, and compressed bodies. These changes allowed them to hunt more effectively and navigate the extreme scarcity of food.
Despite these adaptations, the study found that anglerfish display an incredible variety of shapes and sizes, from the round, globular forms we often associate with anglerfish to long, slender types with trap-like jaws.
Diversity in a resource-poor world
The surprising finding of the study is how much anglerfish diversified despite living in the bathypelagic zone, an environment with little food and no sunlight.
Typically, scientists expect more diversity in habitats with lots of physical features, like coral reefs or rocky seafloors, where animals can interact with their surroundings.
Yet anglerfish managed to achieve high levels of variation even in the featureless, open waters of the deep sea.
“Anglerfish are one of the few examples of how life can diversify so dramatically in such an extreme environment,” says Evans. Their unique features, such as bioluminescent lures and wide jaws, may have given them an edge in exploiting limited resources. However, the researchers suggest that random genetic changes or relaxed evolutionary pressures might also explain the variety in their body shapes.
A window into evolution and adaptation
The team used a combination of genetic data, 3D scans, and fossil records to reconstruct the evolutionary history of anglerfish.
By analyzing 132 species, representing 38% of all known anglerfish, they mapped out how these creatures adapted to their environments over time. Their findings also revealed that coastal anglerfish, like frogfish, evolved much more slowly than their deep-sea relatives.
This study offers more than just an understanding of anglerfish. It shows how life can adapt in unexpected ways, even in the most challenging conditions.
The deep sea, one of Earth’s least-explored ecosystems, plays a critical role in global biodiversity and the carbon cycle. Learning how anglerfish survive in such conditions can help scientists predict how life might respond to environmental changes, including those driven by climate change.
“Anglerfish show how evolution can be incredibly creative under constraints,” Evans says. “Their story is not just about survival—it’s about innovation in the face of adversity.”
