Walking fish

Walking fish, sometimes called ambulatory fish, is a general term that refers to fish that are able to travel over land for extended periods of time. The term may also be used for some other cases of nonstandard locomotion of fish, e.g., when describing fish "walking" along the sea floor.

Types of walking fish

Most commonly this term is applied to amphibious fish. Able to spend longer times out of water, these fish may use a number of means of locomotion, including springing, snake-like lateral undulation, and tripod-like walking. The mudskippers 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 [http://www.cairnsmuseum.org.au/tourism.htm] . 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 plates and pushing itself by its fins and tail. Some reports indicate that it can also climb trees Fact|date=February 2007.

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 that allows them to live out of water for several days. Some are invasive species. A notorious case in the United States is the Northern snakehead. [ [http://news.nationalgeographic.com/news/2002/07/0712_020712_snakehead.html "Maryland Suffers Setback in War on Invasive Walking Fish"] , "National Geographic News"
July 12, 2002] Polypterids have rudimentary lungs and can also move about on land, though rather clumsily.

There are some species of fish that can "walk" along the sea floor but not on land. One such animal is the flying gurnard, which can walk on the sea floor. (It does not actually fly, and should not be confused with flying fish.) The batfishes of the Ogcocephalidae family (not to be confused with Batfish of Ephippidae) are also capable of walking along the sea floor.

The axolotl, an aquatic salamander native to Mexico, is colloquially known as the "Mexican walking fish", although it is not a fish.

Evolutionary link

In modern fish the "walking" ability differs from that of tetrapods. The theory of evolution suggests that life originated in the oceans and later moved onto land, and paleontologists have long been looking for a missing evolutionary link between ocean-living and land-living animals. Of recent finds, reported in "Nature" (April 2006) is "Tiktaalik roseae", which has many features of wrist, elbow, and neck that are akin to those of tetrapods.cite journal | quotes=no | journal = Nature | volume = 440 | pages = 757–763 | date = 6 April 2006 | doi = 10.1038/nature04639 | title = A Devonian tetrapod-like fish and the evolution of the tetrapod body plan | url = http://www.nature.com/nature/journal/v440/n7085/abs/nature04639.html | author = Edward B. Daeschler, Neil H. Shubin and Farish A. Jenkins, Jr] . It belonged to a group of lobe-finned fishes called "Rhipidistia", which according to some recent theories were the ancestors of all "tetrapods" (four-legged animals).

Popular culture

Another usage of the term "walking fish" is in reference to the "Darwin fish", a bumper sticker parody of the Ichthys, a symbol of Christianity.

References