Shedd Aquarium

Frogfish Scientific Name: Antennarius sp.

Sitting completely still among colorful corals and sponges, a frogfish patiently waits for prey to approach. Wiggling a small fish-shaped lure that hangs off a ‘fishing pole’ from its forehead, the frogfish attracts curious creatures into its striking zone. Before they even know it, the prey is swallowed by the well camouflaged frogfish.

Region: Philippines

Taxon: Fish

Appearance
Spots, stripes, fringe, whiskers, warts and tassels on prickly skin cryptically conceal frogfish from predators and help them ambush prey. With body shapes and colors very similar to corals and sponges in shades of yellow, cream, orange, red, green, brown and black, frogfish wait nearly invisible for prey to come to them. Most frogfish change color to match their surroundings over periods ranging from a few minutes to a few days.

Frogfish can walk using jointed elbow-like pectoral fins or fins pairs on the sides of the body behind the gills. They are used like legs to actually move the fish around the reef, and have what actually looks like feet and toes.

Frogfish from the Family Antennariidae can be as small as 1.7 inches (4.3 cm) and as large as 15 inches (38cm).

Habitat
Most frogfish live on protected coastal tidepools, lagoons, and coral reefs at depths of 3 feet (1 m) or less but can be found to depths of 250 feet (75 m). They hide among brightly colored corals, sponges and algae on the reef. They can also be found near mangroves in brackish water or even in freshwater areas.

Range
Frogfish live in the warm parts of the Pacific Ocean and the Red Sea.

Diet
Frogfish wriggle an illicium or a “fishing pole" tipped with a fleshy “lure" that sticks out of their forehead and hangs above their mouth to attract fish. The bulbous bodies of these small round fish swell, enabling them to swallow their prey whole. Their food may even be larger than the frogfish’s body. Frogfish can open their large mouths—at least twelve times their normal size. If a fish is longer then their body, they fold the prey fish up inside their expanding stomach. Projecting their mouth forward, frogfish suck in prey with such force that it only takes six-thousandths of a second. Other animals can’t even see an animal get eaten by the frogfish, making them unaware it’s even there.

If the “lure" or esca is bitten off by a prey fish, the frogfish can actually regrow its missing esca. It will take between three and six months to regenerate and will look exactly like the original one. If the illicium is damaged, the frogfish may even grow a second illicium and then have two different escas. When the frogfish isn’t ‘fishing’ the illicium lays flat back against the frogfish’s head.

Reproduction
At night during mating season, female frogfish begin to swell when their eggs are ready to be fertilized. The male signals he is ready to mate by shaking and spreading his fins. Then the pair darts for the water’s surface where the female shoots the eggs out and the male fertilizes them. This happens every three to four days during mating season, and a female can produce thousands of tiny eggs each time. The eggs are clustered inside in an egg raft which is a large heap of thick jelly that contains the eggs. The female heads back down to the reef to rest and the male takes the egg raft and sticks it to the side of his body. The eggs are then safely guarded by the male until they hatch. In some species of frogfish, the female cares for the eggs instead of the male.

>A species or group of organisms that is in danger of extinction or disappearing from the face of the earth in the near future if its situation is not improved.

A species that can be found throughout its natural range but is declining in number and may become endangered in the absence of special protection efforts.

A species that is not declining in number but is of special concern because it is sensitive to pressure by particular human activities or natural events.

A species that is not declining in number and is not sensitive to pressures by human activities or natural events.

Threats and Management
Frogfish can be troublesome for the home aquarist. They are cannibals, which means they will eat their own kind. Putting two of them in a home aquarium together often results in one getting eaten by the other.

They also like to hang out by corals, sometimes sitting on top of them and keeping them from being able to extend their polyps. Frogfish will eat any fish that is not at least twice as big as they are. Since frogfish are difficult to keep by the home aquarist, they are not frequently acquired by the pet trade.

Did You Know?
Frogfish can gulp down water to puff out like the porcupinefish or pufferfish. This prevents larger animals from being able to swallow their huge bloated bodies.

A frogfish can also move by forcing jets of water out of its gills, propelling it forward. If the frogfish needs to move really fast, it can also quickly beating its caudal fin or tail fin.

The esca of the frogfish varies in its shape from species to species. The esca of the striated frogfish looks like a worm, while the wartskin frogfish has an esca that resembles a small fish.

Young wartskin frogfish and painted frogfish will change their color and movements to mimic a poisonous sea slug. This protects them from being eaten by large predators that will think they are the slug instead of a frogfish.

Some home aquarium keepers buy brightly colored frogfish only to get them into their own aquarium and see them turn a drab brown color. Remember, frogfish blend in with their surroundings. If a home aquarium is filled with drably colored rocks, the frogfish will change color to match.

An unusual member of the Family Antennariidae, the two-spot or twin-spot frogfish has the ability to live in either marine or freshwater habitats.

References
Print Publications:
Debelius, H. 1999. Indian Ocean Reef Guide. Frankfurt, Germany: IKAN. 321p.
ISBN# 3-9317-0267-7

Hoover, J.P. 1993. Hawaii’s Fishes. A Guide for Snorkelers, Divers and Aquarists. Honolulu, Hawaii: Mutual Publishing. 183p. ISBN# 1-56647-001-3.

Michael, S.W. 1998. Reef Fishes. Shelburne, Vermont: Microcosm. 624p.
ISBN# 1-890087-21-1.

Myers, R.F. 1999. Micronesian Reef Fishes. Barrigada, Guam: Coral Graphics. 216p.
ISBN# 0-9621564-4-2

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

Reader’s Digest. 1984. Reader’s Digest Book of the Great Barrier Reef. Sydney, Australia: Reader’s Digest Services Pty Limited. 384p. ISBN# 0-949819-41-7.

Vocabulary Words

Cannibal – An organism that eats others of its own species.

Caudal – Having to do with the end or tail of an animal. The tail fin.

Egg raft – A large heap of thick jelly that contains eggs.

Epipelagic zone – The zone of the open ocean near the surface.

Esca – The lure on the illicium on a frogfish.

Extinction – An organism that has not been present on the face of the earth for over 50 years.

Illicium – The first dorsal spine of a frogfish which is modified into a fishing pole tipped with an esca or lure.

Organism – A living thing.

Pectoral – The paired fins on the sides of a fish behind the gills.

Species – A group of organisms capable of breeding and producing fertile offspring; organisms that share the same gene pool.