Fish
Frogfish
Antennariidae · also called frogfish, anglerfish (shallow-water)
A frogfish is a fish pretending to be furniture. It sits on a reef looking like a lumpy sponge or a clump of algae, barely moving for hours, until something swims close enough — and then it performs one of the fastest strikes in the animal kingdom and swallows a fish sometimes bigger than itself.
Overview
Frogfish — family Antennariidae, about 50 species — live on shallow reefs, sponge gardens, and weedy or rubble bottoms in warm seas worldwide, with one species, the sargassumfish, living out in floating rafts of ocean seaweed. They are small (mostly 2–15 cm), rounded, and covered in bumps and skin flaps. They are poor swimmers and spend almost all their time sitting still.
The lure
The first spine of the dorsal fin is modified into a fishing rod (the illicium) tipped with a fleshy bait (the esca) shaped, depending on species, like a worm, a shrimp, or a small fish. The frogfish twitches the lure to draw prey within range.
The strike
When prey comes close, the frogfish opens its mouth explosively, expanding the volume inside up to twelvefold, and the sudden inrush of water sucks the victim in. The strike is timed at about 6 milliseconds — one of the fastest feeding movements of any vertebrate — and the frogfish can engulf prey as large as itself. It has a highly distensible stomach and often eats other frogfish.
Camouflage and “walking”
Frogfish skin can change colour over days to match the background, and many species mimic sponges exactly, texture and pore-pattern included. To get around, a frogfish walks across the bottom on limb-like pectoral and pelvic fins with an elbow-like joint — a slow trudge or a two-fin “gallop” — or jets itself along by pumping water out through its gill openings.
Anglerfish relatives
Frogfish are shallow-water anglerfish (order Lophiiformes), close kin of the deep-sea black anglerfish and of the monkfish sold as food.
Status
Most frogfish species have not been individually assessed; as a group they are widespread and locally common, dependent on healthy reef and sponge habitat.
Frogfish: common questions
How does a frogfish catch its food?
By ambush, aided by a built-in fishing rod. A frogfish sits motionless, camouflaged, often for hours. Projecting from its forehead is a slender rod — a modified fin spine — with a fleshy lure on the end shaped like a small worm, shrimp, or fish, which the frogfish wiggles enticingly. When a curious fish comes to investigate the "bait," the frogfish strikes — it flings its mouth open, expanding the space inside up to twelve times, and the resulting inrush of water sucks the prey straight in. The whole strike takes about six thousandths of a second, among the fastest movements of any vertebrate, and is far too quick for the prey — or a human eye — to follow.
Can frogfish really walk?
Yes, in their own way. Frogfish are poor swimmers, and instead they use their thickened pectoral and pelvic fins, which have a joint resembling an elbow, to clamber slowly over the seabed. Depending on the species and the surface, this looks like a slow walk or a bounding "gallop" in which both pectoral fins move together. For a quick getaway a frogfish can also take in water through its mouth and force it out through small gill openings behind its fins, jetting itself forward.
How good is frogfish camouflage?
Among the best of any fish. Their skin is covered in bumps, wart-like lumps, and hair- or frond-like appendages, and it can slowly change colour over days or weeks to match the background. Many species imitate sponges — sometimes a particular species of sponge — down to the texture and the pattern of pores, and some sit among matching sponges where they are effectively invisible. Others mimic algae-covered rocks or coral rubble. The disguise works on both the prey they are trying to eat and the larger predators that might eat them.
Are frogfish related to deep-sea anglerfish?
Yes. Frogfish belong to the order Lophiiformes, the anglerfishes, and share the group's signature feature — the fishing-lure fin spine. Frogfish are essentially the shallow-water, reef-dwelling members of the anglerfish radiation, whereas the famous black, bioluminescent-lure anglerfish with the tiny parasitic males live in the deep sea. Goosefish or monkfish, sold as food, are another branch of the same order.