Frogfish

Frogfishes are any member of the anglerfish family Antennariidae, of the order Lophiiformes. Antennariids are known as anglerfishes in Australia, where the term 'frogfish' refers to members of the unrelated family Batrachoididae. Frogfishes are found in almost all tropical and subtropical oceans and seas around the world, the primary exception being the Mediterranean Sea. Frogfishes are small, short and stocky, and sometimes covered in spinules and other appendages to aid in camouflage. The camouflage aids in protection from predators and enables them to lure prey. Many species can change colour; some are covered with other organisms such as algae or hydrozoa. In keeping with this camouflage, frogfishes typically move slowly, lying in wait for prey, and then striking extremely rapidly, in as little as 6 milliseconds. Few traces of frogfishes remain in the fossil record, though Antennarius monodi is known from the Miocene of Algeria and Eophryne barbuttii is known from the Eocene of Italy. Frogfishes live in the tropical and subtropical regions of the Atlantic and Pacific, as well as in the Indian Ocean and the Red Sea. Their habitat lies for the most part between the 20 °C isotherms, in areas where the surface level water usually has a temperature of 20 °C (68 °F) or more. They extend beyond the 20 °C isotherms in the area of the Azores, Madeira and the Canary Islands, along the Atlantic coast of the United States, on the south coast of Australia and the northern tip of New Zealand, coastal Japan, around Durban, South Africa, and at Baja California, Mexico. The greatest diversity of species is in the Indo-Pacific region, with the highest concentration around Indonesia. In the small Lembeh Strait, north-east of Sulawesi, divers have found 9 different species. Frogfish live generally on the ocean floor around coral or rock reefs, at most to 100 m (330 ft) deep. A few exceptions to these general limits are known. The brackishwater frogfish is at home in ocean waters as well as brackish and fresh water around river mouths. The sargassum fish lives in clumps of drifting sargassum, which often floats into the deeper ocean and has been known to take the sargassum fish as far north as Norway. Frogfishes have a stocky appearance, atypical of fish. Ranging from 2.5–38 cm (0.98–14.96 in) long, their plump, high-backed, unstreamlined body is scaleless and bare, often covered with bumpy, bifurcated spinules. Their short bodies have between 18 and 23 vertebrae and their mouths are upward-pointed with palatal teeth. They are often brightly colored, white, yellow, red, green, or black or spotted in several colors to blend in with their coral surroundings. Coloration can also vary within one species, making it difficult to differentiate between them. Rather than typical dorsal fins, the front-most of the three fins is called the illicium or 'rod' and is topped with the esca or 'lure'. The illicium often has striped markings, while the esca takes a different form in each species. Because of the variety of colours even within a single species, the esca and illicium are useful tools to differentiate among different varieties. Some of them resemble fish, some shrimp, some polychaetes, some tubeworms, and some simply a formless lump; one genus, Echinophryne, has no esca at all. Despite very specific mimicry in the esca, examinations of stomach contents do not reveal any specialized predation patterns, for example, only worm-eating fish consumed by frogfishes with worm-mimicking esca. If lost, the esca can be regenerated. In many species, the illicium and esca can be withdrawn into a depression between the second and third dorsal fins for protection when they are not needed. Frogfish have small, round gill openings behind their pectoral fins. With the exception of Butler's frogfish and the rough anglerfish, frogfish use a gas bladder to control their buoyancy.