That Glowing Lure On The Anglerfish? Scientists Traced Its 72-Million-Year History

Few predators hunt quite like the anglerfish. Rather than chasing prey, it waits, dangling a fleshy lure from the top of its head like a tiny beacon, coaxing smaller fish to swim directly into its waiting jaws. It’s a fish that fishes. A new study in Ichthyology & Herpetology has now reconstructed the evolutionary history of that built-in fishing rod, revealing when it first appeared, how it changed over tens of millions of years, and why the most elaborate versions may have evolved for reasons well beyond catching a meal.

Researchers Alex J. Maile of the University of Kansas and Matthew P. Davis of St. Cloud State University examined 118 anglerfish specimens representing 102 species across 13 families. Using a fossil-calibrated family tree that integrated genetic data and roughly 100 morphological traits, they traced how different lure types arose and diversified across the entire anglerfish group. What they found reshapes understanding of one of the ocean’s strangest animals.

Anglerfish are far more diverse than most people realize. The group includes not just the nightmare-inducing deep-sea species made famous by Finding Nemo, but also monkfish, a seafood menu staple, and colorful frogfish beloved by divers. All of them share a version of the same lure structure: a modified fin spine called the illicium, tipped with a fleshy bait piece called the esca. How that structure works, and how ornate it becomes, varies dramatically across species and habitats.

Inside the Anglerfish’s Tackle Box

Anglerfish lures fall into three functional categories: mechanical, chemical, and bioluminescent. Mechanical lures rely on motion and mimicry, wiggling to imitate a worm or small crustacean. Chemical lures release attractants from the esca to draw prey within striking range. Bioluminescent lures glow, powered by light-producing bacteria living inside the tissue. In the famous deep-sea species, that glow is the only light source for miles in any direction.

Mechanical lures are the oldest of the three. Fossil calibrations place the common ancestor of all anglerfish at roughly 72 million years ago, in the Late Cretaceous, before the mass extinction that ended the age of non-avian dinosaurs. Chemical luring evolved independently twice: once in batfishes and separately in a single frogfish species, Antennarius striatus. Bioluminescent lures appeared just once, arising in a deep-sea anglerfish lineage during the Oligocene epoch, associated with a transition into deep, open-water environments. Some lineages within that group later lack bioluminescence and rely on non-luminous lures.

Moving into pitch-black open water created strong pressure to evolve new hunting tools. A glowing lure is nearly irresistible to curious prey in total darkness, but it also risks illuminating the anglerfish itself. Deep-sea species appear to have solved this by evolving longer lures, increasing the gap between the glowing tip and their own bodies. Species with bioluminescent lures carry much longer lure components relative to body size than those with mechanical lures alone.

Lure length and mobility also track closely with habitat and behavior. Some whipnose anglerfish carry lures longer than their own bodies. Getting prey within striking distance when the lure extends that far out front is a logistical problem, and observations suggest these species may compensate by swimming inverted, directing the lure downward and diving into prey from above. At the opposite extreme, coffinfishes have some of the shortest lures of any anglerfish, barely reaching the mouth, but they can angle them vertically to attract prey hovering directly overhead.

When an Anglerfish Lure Becomes a Mating Signal

Perhaps the most unexpected finding involves what the lure does beyond hunting. Among deep-sea ceratioid anglerfish, males are dramatically smaller than females and lack lures entirely. Instead, they have enlarged eyes and highly developed olfactory systems, apparently tuned to detect the glow and chemical signals of female lures from a distance.

Anglerfish lineages with bioluminescent lures showed significantly higher rates of species diversification than those with mechanical or chemical lures, while the one species lacking a lure in both sexes showed the lowest diversification rates observed. That pattern has also been seen in some other bioluminescent fish, where species-specific light signals appear to help animals identify mates of their own kind and may accelerate the formation of new species over time.

Put another way, the lure may be pulling double duty: catching prey in the dark while also serving as a mate-recognition signal. Whether females evolved increasingly elaborate glowing lures to attract males, or whether males developed sharper senses in response to female displays, remains unresolved. The researchers describe this as a hypothesis supported by anatomy and diversification data, not a settled conclusion.

Why the Anglerfish Still Has Scientists Hooked

Every version of the anglerfish lure, whether the wiggling decoy of a shallow-water frogfish, the chemical bait of a seafloor batfish, or the glowing beacon of a deep-sea species, reflects millions of years of adaptation shaped by habitat, predation, and reproduction. Scientists are now beginning to read that record in detail, one lure at a time.

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