Frogfish

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Frogfish
Striped frogfish (Antennarius striatus), blue eye, white esca in the shape of a worm

Striped frogfish ( Antennarius striatus ),
blue eye, white esca in the shape of a worm

Systematics
Acanthomorphata
Spinefish (Acanthopterygii)
Perch relatives (Percomorphaceae)
Order : Armfinch (Lophiiformes)
Subordination : Sensorfish-like (Antennarioidei)
Family : Frogfish
Scientific name
Antennariidae
Berg , 1958

The family of anglers or sensor fish (Antennariidae) currently includes 49 previously described species usually relatively small and well camouflaged, plumper bonefish from the order of anglerfish (Lophiiformes). In contrast to the related deep-sea frogfish (Ceratioidei), frogfish live in the shallow water of tropical and subtropical seas. They are scaly and show as a typical feature a "fishing rod" ( Illicium ) formed from the first hard ray of the dorsal fin with attached bait ( Esca ).

distribution

The 20 degree isotherms limit the approximate range of the frogfish

Frogfish live in tropical and subtropical regions in the Atlantic and Pacific , in the Indian Ocean , in the Red Sea , but not in the Mediterranean . Their distribution area lies largely between the 20-degree isotherms , the areas in which the surface water usually has a temperature of at least 20 ° C. In the area of ​​the Canary Islands , the Azores and Madeira , on the Atlantic coast of the USA , the south coast of Australia , the northern tip of New Zealand , near Japan , near Durban in South Africa and on the Baja California , however, they exceed the 20-degree isotherms.

Most of the species are in the Indo-Pacific, with the main distribution around the islands of Indonesia . In the Lembeh Straits northeast of Sulawesi , divers have found nine species in a confined space. There are six species in the Atlantic , three of which are endemic . The brackish frogfish ( Antennarius biocellatus ) is native to the seas around Indonesia, New Guinea , the Philippines , Taiwan, and the Solomon Islands and also goes into the brackish and fresh water of the estuaries. With one exception, frogfish live on the seabed on coral and rock reefs at depths of up to 100 meters. The Sargassum frogfish ( Histrio histrio ) is found in pelagic drifting tails in all oceans and is often drifted with them into colder waters up to the coast of Norway .

features

Antennarius striatus

Frogfish have a squat appearance that is completely untypical for fish. The plump, high-backed, non-streamlined body is scaly and bare or provided with forked skin protrusions , the spinulae . The animals are often wonderfully colorful, white, yellow, red, green or black, but also spotted in different colors and thus camouflaged in their colorful reef biotope. The coloring is also very variable within a species and the species are difficult to distinguish. The short body has 18 to 23 vertebrae. The mouth is large and slanted. Frogfish have palatal teeth .

Of the three hard rays of the dorsal fin , the first was transformed into a fishing rod (Illicium) with attached bait (Esca). The Illicium often has a striped drawing. The Esca has a different shape in the individual frogfish species and is an important distinguishing feature between the species. It sometimes resembles a fish, a shrimp , a bristle or tube worm , or is simply a misshapen tuft. However, one could not specialize in certain gastric examinations, e.g. B. only find prey fish that eat worms. If lost, the Esca can be regenerated. The genus Echinophryne has no esca. In many species, Illicium and Esca can be placed in a recess on the second and third dorsal fin rays for protection when not in use. Both dorsal fin rays are enlarged and covered with skin. The soft rayed part of the dorsal fin has 10 to 16 fin rays, the anal fin 6 to 10. The pectoral and ventral fins are short, have strong fin rays and resemble hands. The throaty ventral fins are located in front of the pectoral fins. The pectoral fins have 6 to 14 fin rays. The pectoral fin muscles , 8 abductors and 5 adductors , are well developed. The small, round gill openings lie behind the pectoral fins . Frogfish grow to be 2.5 to 38 centimeters. With the exception of the genera Kuiterichthys and Tathicarpus , frogfish have a swim bladder .

Autapomorphies , which distinguish the frogfish from the related families from the subordination of the antennae-like (Antennarioidei), are the shortened body, the S-shaped curved spine and the enlarged third dorsal fin spine with the associated pterygiophore .

Mimicry and camouflage

The purpose of the peculiar shape of the frogfish is to make them invisible and to fool potential prey into a source of food. In behavioral research, this is called Peckham's or attack mimicry . The frogfish are disguised as overgrown stones, corals, sponges or sea squirt because of their misshapen shape, color and skin tags . The latter have spots at the points of the openings of the sponges or sea squirts. In 2005, a black form of the striped frogfish ( Antennarius striatus ) was discovered that mimics sea ​​urchins . Some frogfish are also overgrown with algae or small hydroid polyps . The camouflage is so perfect that nudibranchs crawl over the animals.

A frogfish disguised as algae rock

The camouflage seems to be important for the scale-less and defenseless frogfish in addition to the function as attack mimicry but also as protection against predators. Frightened and clearly visible frogfish were attacked immediately by damselfish , wrasse and other fish both in aquariums and in the wild and were killed at least in the aquarium. Frogfish can also bloat by ingesting water in their stomachs like puffer fish .

Many frogfish can change the color of their skin and are usually light and dark in color. The light is usually yellow or yellow-brown, the dark green, black or dark red. Most frogfish show themselves with fair skin. The color change takes a few days to several weeks. What triggers the color change is still unknown.

The Sargassum frogfish has developed a special adaptation . It lives in the Atlantic and Indo-Pacific between stocks of algae and drifting seaweed of the genus Sargassum , where it can hold onto its fins and climb around. Its coloring and numerous skin attachments camouflage it in its habitat , which it never leaves.

Locomotion

Frogfish are true to their location. They lie still on the ocean floor most of the time, waiting for prey. If they spot one, they can use their pectoral and pelvic fins to slowly approach the prey. You have two “gaits” at your disposal. You can take turns moving the pectoral fins forward and using them like a two-legged terrestrial vertebrate . The pelvic fins play no role here. On the other hand, they can move in a kind of slow gallop . They move both pectoral fins back and forth simultaneously and temporarily support their body weight on the pelvic fins as the pectoral fins move forward. They only hold out both gaits for short distances.

In the open water, frogfish swim with flaps of the tail fin. They also have a type of “ jet propulsion ” that is particularly often used by young frogfish. To do this, they squeeze the breath water taken in with their mouths in jerks in the rhythm of breathing from the narrow gill openings located far back near the base of the pectoral fin.

Catching prey

Yawning Painted Frogfish ( Antennarius pictus )

Frogfish eat shrimp and fish, including other species. A potential prey is first observed and followed with the eyes. When the frogfish approaches seven times its length, it begins to move the rod in the manner of the movement pattern of the animal represented by the Esca. If the Esca is in the shape of a worm, it moves sinusoidally, like the swimming movements of bristle worms. The frogfish presses itself flat against the ground. If the victim is only one body length away, the frogfish turns into a position that is favorable for snapping shut. The prey is caught by suddenly opening the mouth. This increases the volume of the oral cavity six times and tears the victim into the mouth with water. The water flows back out through the gills while the prey is swallowed and the esophagus is closed by a sphincter muscle to prevent the victim from escaping.

Slow motion recordings have shown that opening the mouth takes only six milliseconds, a time in which a muscle cannot contract at all. For this reason, a previously unknown biomechanical process in the jaw is suspected that can store energy and suddenly release it.

The prey of the frogfish can even be somewhat larger than they are. So far, two photographs have been taken of how frogfish swallowed lionfish . The poison in the hard fin spines of this unusual prey doesn't seem to have bothered them.

Reproduction

Frogfish in the sea off East Timor

The reproductive behavior of the normally solitary frogfish has not yet been sufficiently researched. There have been few observations on animals living in aquariums, and even less from the ocean. Most frogfish are free spawners . A few days to eight hours before the eggs are laid, the female's abdomen swells because the eggs absorb water. The male approaches the female about two days before the spawning process. It is not known whether spawning is triggered by an external trigger such as the phases of the moon , or whether the male is attracted by an odor given off by the female. In all the couples observed so far, one partner was significantly larger, sometimes even ten times. If one could determine the sexes, then the great individual was always the female. Spawning always takes place after dark.

In courtship, the male first swims after the female, touches it with its mouth and always stays near the cesspool . Then it swims parallel to the female, touches it with a pectoral fin and begins to tremble, to which the female also reacts with tremors. Shortly before spawning, the female stretches out all her fins, begins to swim across the ocean floor and lifts her heavily swollen abdomen. Suddenly the partners swim up into the open water and expel eggs and sperm at the highest point. Sometimes the male should pull the eggs out of the cloaca with his mouth. Both fish swim to the bottom and separate immediately because the smaller male may otherwise be eaten by the female.

The eggs are 0.5 to one millimeter in size and hang together in a gelatinous mass or ribbon, which in the Sargassum frogfish can be up to three meters long and 16 centimeters wide. It can be 48,000 to 280,000 eggs. In most species, the egg ball floats on the sea surface. The larvae that hatch after two to five days are between 0.8 and 1.6 millimeters long and live on the yolk sac for the first four days. They have long fin filaments and thus resemble tiny tentacle-bearing jellyfish. The larvae live planktonically for one to two months . After that, with a length of 15 to 28 millimeters, they already have the shape of the adult fish and change to life on the sea floor. Young frogfish often imitate poisonous nudibranchs and flatworms in color . First live in shallow water between algae, seaweed and sponges.

Some subtropical species from the genera Lophiocharon , Phyllophryne , Rhycherus are substrate spawners and practice brood care , mostly the male. The male of the three-cornered frogfish ( Lophiocharon trisignatus ) carries around 600 large eggs glued to his body. Only in the tassel frogfish ( Rhycherus filamentosus ) does the female guard the brood. The Australian genus Histiophryne carries the eggs around with the help of the pectoral fins.

Tribal history

There are hardly any fossil remains of the frogfish. In the northern Italian Monte Bolca formation, which arose from Tethys deposits in the middle Eocene , the only three centimeter long Histionotophorus bassani was found , which was initially described as a frogfish. Today, however, Histionotophorus is considered a synonym of the recent genus Brachionichthys , the only one of the Brachionichthyidae family closely related to the frogfish . The oldest fossil definitely belonging to the frogfish was described as Eophryne barbutii in 2009 . In 2005 a fossil frogfish from the upper Miocene of Algeria was described. Antennarius monodi is said to belong to the Antennarius ocellatus group (today genus Fowlerichthys ) and to be related to the recent Fowlerichthys senegalensis .

Systematics

External system

Systematically, the frogfish belong to the arm finfish (Lophiiformes), a group of real bony fish (Teleostei) that have adapted to life on the seabed or in the deep sea as ambulance hunters. The armflossers have so far been counted among the Paracanthopterygii , which together with the cod-like fish also include important food fish such as cod and haddock . Today, however, the traditional paracanthopterygii are regarded as polyphyletic . More recent molecular genetic studies place the armfin fins among the perch relatives , the main group of the barbed fins , which without the inclusion of the old Paracanthopterygii orders would be polyphyletic frogfish (Batrachoidiformes), viscera-like (Ophidiiformes) and armfin fish .

Within the anglerfish anglers fish form with three others, species-poor families along the taxon of the probe-like fish (Antennarioidei). Together with deep-sea frogfish , sea ​​toads and sea ​​bats, these form an unnamed taxon, which is the sister group of the anglerfish (Lophioidei), the most primitive armfin fish .

Melanocetus johnsonii , a deep-sea frogfish

The following illustration shows the position of the frogfish within the armfinch:

 Armfinch  (Lophiiformes)  

 Monkfish (Lophioidei)


  NN  

 Deep-sea frogfish (Ceratioidei), sea ​​toads (Chaunacoidei)
 and sea ​​bats (Ogcocephalioidei)


  Sensorfish-like  (Antennarioidei)  

 Hand fish or wart anglers (Brachionichthyidae)


  NN  

 Lophichthyidae


  NN  

 Tetrabrachiidae


   

 Frogfish (Antennariidae)







Internal system

Of the 165 species previously described in the last two centuries, fewer than 50 species have remained after a family revision . Different color forms of a species were often viewed as separate species. The American ichthyologist Theodore Pietsch has announced the description of other species.

Within the frogfish two main clades can be distinguished, which are classified as subfamilies, the Antennariinae with five genera and 30 species and the Histiophryninae , which contain nine genera and 19 species. About half of the species belong to the genera Antennarius and Antennatus , which are further divided into groups of species.

Fowlerichthys ocellatus
Antennarius commerson
Histrio histrio
Antennatus tuberosus
Antennatus nummifer
Lophiocharon hutchinsi
Histiophryne psychedelica

Aquarium keeping

Occasionally, frogfish for keeping in saltwater aquariums are offered in specialist shops. However, the fish are not very durable and often refuse to feed or become fat if they do eat it. They usually die within a year, with most surviving no more than half a year. In the Aquazoo Düsseldorf and Vivarium Karlsruhe , however, they had more success and kept frogfish for four years.

Sources and further information

Individual evidence

Most of the information in this article is taken from the sources given under literature, and the following sources are also cited:

  1. ↑ Frogfish on Fishbase.org (English) ( Kuiterichthys pietschi and Porophryne erythrodactylus are not yet listed there.)
  2. ↑ a b c Frank Scheidewind: Frogfish, family Antennariidae , in Koralle No. 38
  3. ^ A b Rachel J. Arnold, Theodore W. Pietsch: Evolutionary history of frogfishes (Teleostei: Lophiiformes: Antennariidae): A molecular approach. Molecular Phylogenetics and Evolution, Volume 62, Issue 1, January 2012, pages 117–129 doi : 10.1016 / j.ympev.2011.09.012
  4. ↑ a b c d Scott Michael: Behavioral observations on frogfish , in Koralle No. 38
  5. ↑ Peter Nahke: Tricks in the reef: camouflage, deception and partnerships . Year, Hamburg 1998, ISBN 3-86132-243-9
  6. ↑ a b Ellen Thaler : Experiences with frogfish and thoughts on keeping , in Koralle No. 38
  7. ↑ Video at Spiegel online (shows a running frogfish (wrongly called a dotted hand fish))
  8. ↑ a b T. W. Pietsch, DB Grobecker: Fühlerfische , in Biologie der Meere, 1991, Spektrum Akad. Verl., ISBN 3-89330-753-2
  9. ^ Karl A. Frickhinger: Fossil Atlas. Pisces , Mergus, 1991, ISBN 3-88244-018-X
  10. ^ Pietsch, Theodore W. and Kenaley, Christopher P. 2005. Lophiiformes . Version 18 October 2005 (Tree of Life Web Project)
  11. ^ G. Carnevale, TW Pietsch: An eocene frogfish from monte bolca, italy: the earliest known skeletal record for the family . Palaeontology, Vol. 52, Part 4, 2009, pp. 745-752. (PDF; 427 kB)
  12. ^ G. Carnevale, TW Pietsch: Filling the gap: a fossil frogfish, genus Antennarius (Teleostei, Lophiiformes, Antennariidae), from the Miocene of Algeria . Journal of Zoology, Vol. 270, 2006, pp. 448-457. doi : 10.1111 / j.1469-7998.2006.00163.x
  13. ↑ David Johnson and E. 0. Wiley: Percomorpha , Version 09 January 2007 (Tree of Life Web Project)
  14. ↑ David Johnson and E. 0. Wiley: Acanthopterygii , Version 09 January 2007 (Tree of Life Web Project)
  15. ↑ Frank Scheidewind: Species overview : Frogfish of the family Antennariidae , in Koralle, No. 38
  16. ↑ Peter Bucher: zoo animal keeping 5. Fish . German Harri GmbH, 2005, ISBN 3-8171-1352-8

literature

Web links

Commons : Frogfish  - Collection of images, videos and audio files
This article was added to the list of excellent articles on June 16, 2007 in this version .