A walking fish, or ambulatory fish, is a

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

that is able to travel over land for extended periods of time. Some other modes of non-standard

fish locomotion Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body a ...

include "walking" along the

sea floor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

, for example, in

handfish Handfish are any anglerfish within the family Brachionichthyidae, a group which comprises five genera and 14 extant species. These benthic marine fish are unusual in the way they propel themselves by walking on the sea floor rather than swimmi ...

or frogfish.

Types

Most commonly, walking fish are

amphibious fish Amphibious fish are fish that are able to leave water for extended periods of time. About 11 distantly related genera of fish are considered amphibious. This suggests that many fish genera independently evolved amphibious traits, a process known ...

. Able to spend longer times out of water, these fish may use a number of means of locomotion, including springing,

snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...

-like

lateral undulation Undulatory locomotion is the type of motion characterized by wave-like movement patterns that act to propel an animal forward. Examples of this type of gait include crawling in snakes, or swimming in the lamprey. Although this is typically the ...

, and tripod-like walking. The

mudskipper Mudskippers are any of the 23 extant species of amphibious fish from the subfamily Oxudercinae of the goby family Oxudercidae. They are known for their unusual body shapes, preferences for semiaquatic habitats, limited terrestrial locomotion and ...

s are probably the best land-adapted of contemporary fish and are able to spend days moving about out of water and can even climb mangroves, although to only modest heights. The

climbing gourami The Anabantidae are a family of ray-finned fish within the order Anabantiformes commonly called the climbing gouramies or climbing perches. The family includes about 34 species. As labyrinth fishes, they possess a labyrinth organ, a structure i ...

is often specifically referred to as a "walking fish", although it does not actually "walk", but rather moves in a jerky way by supporting itself on the extended edges of its

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

plates and pushing itself by its fins and tail. Some reports indicate that it can also climb trees. The epaulette shark (''Hemiscyllium ocellatum'') tends to live in shallow waters where swimming is difficult, and can often be seen walking over rocks and sand by using its muscular pectoral fins. It lives in areas of great variation in water depth, usually where the tide falls below its location. If it finds itself out of water, it can survive for several hours, and is capable of walking over land to get to water. This means that it is easily observed by beachgoers in its natural range. There are a number of fish that are less adept at actual walking, such as the walking catfish. Despite being known for "walking on land", this fish usually wriggles and may use its pectoral fins to aid in its movement. Walking catfish have a

respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...

that allows them to live out of water for several days. Some are

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

, for example, the

Northern snakehead The northern snakehead (''Channa argus'') is a species of snakehead fish native to China, Russia, North Korea, and South Korea, ranging from the Amur River to Hainan. It has been introduced to other regions, where it is considered invasive. In ...

in the U.S. Polypterids have rudimentary lungs and can also move about on land, though rather clumsily. The mangrove rivulus can survive for months out of water and can move to places like hollow logs. Some species of fish can "walk" along the sea floor but not on land. One such animal is the

flying gurnard The flying gurnard (''Dactylopterus volitans''), also known as the helmet gurnard, is a bottom-dwelling fish of tropical to warm temperate waters on both sides of the Atlantic. On the American side, it is found as far north as Massachusetts (ex ...

(it does not actually fly, and should not be confused with flying fish). The batfishes of the family Ogcocephalidae (not to be confused with batfish of

Ephippidae Ephippidae is a family containing the spadefishes, with about eight genera and a total of 20 marine species. Well-known species include the Atlantic spadefish (''Chaetodipterus faber'') and the reef-dwelling genus ''Platax'', the batfishes, whic ...

) are also capable of walking along the sea floor. '' Bathypterois grallator'', also known as a "tripodfish", stands on three fins on the bottom of the ocean and hunts for food. The African lungfish (''P. annectens'') can use its fins to "walk" along the bottom of its tank in a manner similar to the way amphibians and land vertebrates use their limbs on land. *

Evolutionary link to land vertebrates

Land vertebrates originate in the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

period and are descended from

Sarcopterygian Sarcopterygii (; ) — sometimes considered synonymous with Crossopterygii () — is a taxon (traditionally a class or subclass) of the bony fishes known as the lobe-finned fishes. The group Tetrapoda, a mostly terrestrial superclass includi ...

fish. In 2006, a fossil, '' Tiktaalik roseae'', was found which has many features of its wrist, elbow, and neck that resemble those of tetrapods, supporting the idea that it represents a sister group to tetrapods.

Comparison of fish with tetrapod-like features

A number of fish, both extant and prehistoric, have featured some characteristics related to locomotion that are typical of

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...

Darwin fish

Another usage of the term ''walking fish'' is in reference to the " Darwin fish", a

bumper sticker A bumper sticker is an adhesive label or sticker with a message, intended to be attached to the bumper of an automobile and to be read by the occupants of other vehicles—although they are often stuck onto other objects. Most bumper stickers are ...

parody of the

Ichthys The ichthys or ichthus (), from the Koine Greek, Greek (, 1st cent. AD Koine Greek pronunciation: , "fish") is (in its modern rendition) a symbol consisting of two intersecting arcs, the ends of the right side extending beyond the meeting point ...

, a symbol of Christianity.

Gallery

File:Alticus arnoldorum climbing up a vertical piece of Plexiglas - pone.0011197.s009.ogv, ''Alticus arnoldorum'' climbing up a vertical piece of Plexiglas File:Hemiscyllium_ocellatum_beach.jpg, An epaulette shark clambering over the sand on a beach File:OgcocephalusParvus.jpg, '' Ogcocephalus parvus''

References