Frogfish Lure

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Turns out, Frogfish are even cooler than you thought!

Frogfish are one of those fish nearly all divers are drawn to (provided you can find them). They are weird animals: they look more like a sponge or lump of algae than a fish, they don’t bother swimming but walk across the bottom instead, they can gulp down prey larger than themselves, and they have what is basically a fishing rod stuck to their foreheads. New research has now found that they are even weirder than you already thought, something is up with the lures at the end of their “fishing rod”.

Maarten De Brauwer

 

Frogfish come in all kinds of sizes and shapes and one species that stands out as special, even for a frogfish, is the Hairy Frogfish (Antennarius striatus). Ever popular with divers, the Hairy Frogfish usually has hair-like filaments growing over its body to better camouflage itself an environments with high algal growth. They are active predators, with a worm-like lure they will wave around to attract prey. As anyone who has ever been lucky enough to see them hunt will be able to tell you, this technique is pretty efficient. But there is more to it than meets the (naked) eye.
Maarten De Brauwer

Things change when you go for a fluorescent night dive. Biofluorescence is a recently newly discovered phenomenon in fish, though it is well known in corals. Unlike bioluminescence (where light is produced by the fish), biofluorescence is passive and happens when light that hits an animal (as when using a blue dive torch) is reflected in a different colour. Doing fluo night dives on coral reefs feels like you’re in a 90’s rave and popped the wrong (or right?) kind of pills, with neon greens and reds flashing all over your retinas. Some fish, like lizardfish fluoresce, potentially to communicate with each other.

Maarten De Brauwer

The body of the Hairy Frogfish does not join in these exuberant colour displays (it’s an ambush predator after all), but here is the interesting thing: its lure does! When looking at a Hairy Frogfish with fluo-diving equipment, you’ll notice only one thing, a brightly fluorescent worm-like creature moving up and down. This creature is nothing other than the lure of our frogfish, mimicking the fluorescence that is also seen in the free-swimming worms it pretends to be, attracting fish that can see the fluorescent worms/lure.

This is the first time it has been shown that biofluorescence might be used to attract prey. It remains to be tested if fluorescent lures indeed help Hairy Frogfish catch more prey, but it is a very exciting glimpse into unexplored hunting strategies in the ocean. It also makes you wonder about how much else is happening in the ocean we cannot see (yet)…

To find out more about my studies please visit my online blog and investigate a new World of the tiny, strange and incredible with me!

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About Author

My name is Maarten, I am a marine biologist, dive instructor, and biology teacher. I come from Belgium, but have been traveling the world as a dive instructor and marine biology researcher for nearly 10 years. From a very young age I have been fascinated by the ocean and the creatures that live in it. During my dive travels I developed a passion for the small, camouflaged, or outright weird critters that can be found below the surface. I currently live in Australia, where I do research on the species important for muck diving, such as frogfishes and seahorses. These animals are not only amazing examples of how crazy evolution can get, but are often important for dive tourism and the aquarium trade. The majority of tropical marine biology research focuses on charismatic or large species such as sharks, turtles and dolphins. Many of the less known, small or camouflaged species are equally important, but are barely studied at all. My work will hopefully change some of that and show the world that weird is beautiful too!

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