A walking fish, or ambulatory fish, is a

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

that is able to travel over

land Land, also known as dry land, ground, or earth, is the solid terrestrial surface of Earth not submerged by the ocean or another body of water. It makes up 29.2% of Earth's surface and includes all continents and islands. Earth's land sur ...

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 or

frogfish Frogfishes are any member of the anglerfish family Antennariidae, of the order Lophiiformes. Antennariids are known as anglerfish in Australia, where the term "frogfish" refers to members of the unrelated family Batrachoididae. Frogfishes are f ...

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 know ...

. 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 reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...

-like lateral undulation, 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 (biology), family Oxudercidae. They are known for their unusual body shapes, preferences for semiaquatic habitats, limited terrestria ...

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

mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

s, although to only modest heights. The climbing gourami 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 respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...

plates and pushing itself by its fins and tail. Some reports indicate that it can also climb trees. The

epaulette shark The epaulette shark ('', Hemiscyllium ocellatum'') is a species of longtailed carpet shark of the family (biology), family Hemiscylliidae, found in shallow, tropical waters off Australia and New Guinea (and possibly elsewhere). The common name o ...

(''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 The walking catfish (''Clarias batrachus'') is a species of freshwater airbreathing catfish native to Southeast Asia. It is named for its ability to "walk" and wiggle across dry land, to find food or suitable environments. While it does not tr ...

. 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 is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

, for example, the northern snakehead in the U.S. Polypterids have rudimentary lungs and can also move about on land, though rather clumsily. The

mangrove rivulus The mangrove rivulus or mangrove killifish, ''Kryptolebias marmoratus'' (syn. ''Rivulus marmoratus''), is a species of killifish in the Family (biology), family Rivulidae. It lives in brackish and marine waters (less frequently in fresh water) a ...

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 (it does not actually fly, and should not be confused with

flying fish The Exocoetidae are a family (biology), family of Saltwater fish, marine Actinopterygii, ray-finned fish in the order (biology), order Beloniformes, known colloquially as flying fish or flying cod. About 64 species are grouped in seven genus, ge ...

). The batfishes of the family

Ogcocephalidae Ogcocephalidae is a family of anglerfish specifically adapted for a benthic lifestyle of crawling about on the seafloor. Ogcocephalid anglerfish are sometimes referred to as batfishes,Ephippidae Ephippidae is a family of percomorph fishes, the spadefishes, in the order Moroniformes. These fishes are found in the tropical and temperate oceans of the world, except for the central Pacific. Taxonomy Ephippidae was first proposed as a fami ...

) are also capable of walking along the sea floor. ''

Bathypterois grallator The tripod fish or tripod spiderfish, ''Bathypterois grallator'', is a deep-sea benthic fish in the family Ipnopidae found at lower latitudes. It is now an iconic deep-sea fish, being observed and photographed by submersibles, using elongate ...

'', 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 period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

period and are descended from

Sarcopterygian Sarcopterygii (; )—sometimes considered synonymous with Crossopterygii ()—is a clade (traditionally a class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe-finned fish. These vertebrates ar ...

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 A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

Darwin fish

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

Ichthys The ichthys or ichthus (), from the Greek (, 1st cent. AD Koinē 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 so as to ...

, 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