One of the most intriguing fish in the ocean swims about in near-total darkness dangling a glowing fishing rod from its face.
There are hundreds of different species of anglerfish – some twitch, wiggle or flick their lures, others use bioluminescence, and some use it to give off secret chemical signals.
Known as an illicium, this is a modified dorsal fin spine that extends out of the fish’s head and dangles over its mouth – perfect for luring prey before eating it.
- Scientists drop cameras 9,100m deep off coast of Japan. What they find baffles them
- Humans descend into huge deep-sea canyon for first time ever. What they find is astounding
They may also have another purpose, according to new research published in the journal Ichthyology & Herpetology. "The conventional idea was they’re using this to attract prey,” says the study’s lead author Alex Maile, an evolutionary biologist at the University of Kansas’ Biodiversity Institute and Natural History Museum in a statement.
“We think it’s actually serving a dual purpose, especially in the deep sea, where you’re taking a lure, adding a glowing element to it, and now you can attract food, but you can also attract a potential mate,” he adds. Only female anglerfish have lures.
The scientists followed evolutionary clues to find out more about the anglerfish’s iconic appendage.
“For this particular group of fishes, there’s limited observational data on how they use their lures,” says co-author Matthew Davis, a professor of biology at St. Cloud State University. “Many have never even been filmed or observed alive.”
- 10 deadliest fish on the planet
- 16 strangest fish in the world, including one that can live out of water
The researchers studied 102 different species of anglerfish. They examined specimens and created an evolutionary tree that used fossil evidence to map out when the lure may have changed. They then used computer models to find patterns between the design of this ‘fishing rod’ and the species’ habitat and behaviour.
“This gives us a sense of what kinds of luring strategies exist for open-ocean glowing anglerfishes versus those more inshore,” Davis adds.
The original lure developed in an anglerfish ancestor around 72 million years ago. This used motion but didn’t glow or secrete chemicals. Gleaming lures came onto the scene around 34–23 million years ago.
At around the same time, much more diversity appeared across different anglerfishes. This might be because the bioluminescent lure made it easier for males and females to find each other in the inky waters.
“We see this pattern with other deep-sea groups like lanternfishes, hatchetfishes and dragonfishes. They use light to say ‘here I am’ to communicate within their species,” says Maile. “There have been hypotheses that [females are] using the lure to communicate with males. The males have really big noses and relatively big eyes.”
Species with bioluminescent lures had longer 'rods’, keeping them further from their face. “The bioluminescence can hang farther in front of the fish, probably in a way that doesn’t light up the fish so prey can’t see it,” says Davis.
The scientists still want to find out more about the anglerfish’s use of chemical lures and how members of the same species find each other. Maile adds: “That interaction deserves more attention – how males find or detect females.”
Top image: The Anglerfish species Bufoceratias wedli from the Field Museum of Natural History. Credit: Matthew Davis
More amazing wildlife stories from around the world
- Ghostly footage shows thousands of giant spider crabs crawling all over each other. It's the largest gathering of its kind on Earth
- Why San Francisco Bay has suddenly become a death trap for gray whales
- When a massive iceberg broke free from Antarctica, scientists found something staggering beneath it
- Drone captures Greenland ice tearing open to reveal humungous animal beneath
- Gigantic iceberg breaks free in Antarctica, revealing ghostly mega-nest beneath
