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Fish that survive on land

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Fish gotta walk... A spotted handfish (Brachionichtus hirsutus) preferentially uses its pectoral and pelvic fins to walk on the sea floor.
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“”A fish definitely did not crawl out and evolve lungs and limbs.
—Professor Elizabeth L. Brainerd, Brown University[1]
“”I tell people they’re fish that can’t swim.
—Rachel Arnold[2]

Fish that survive on land or amphibious fish include many organisms of past and present that evolved and adapted to spend time out of water and breathe air. Studying extant (still living, not extinct) fish and fossils from extinct specimen of these taxa helps evolutionary biologists understand how ancestral land vertebrates existed.

Having air-breathing capacity is useful for fish that live in hypoxic (low-oxygen) environments; it allows them to gulp air from the surface without ever going on land. Air breathing has evolved in some form at least 38 separate times independently among fishes, according to Elizabeth Brainerd.[1][3]

Having leg-like appendages is also useful to fish in some environments. Frogfishes (family Antennariidae) and handfishes (family Brachionichthyidae) are poor swimmers and use their fins to walk along the sea floor.[2]

Examples[edit]

Bichirs[edit]

The bichirs along with the reedfishes are a truly ancient group of fish, diverging from the rest of the ray-finned fish four hundred million years ago. They have both gills and lungs, and while they prefer to live in water, bichirs raised on land can adapt to walking on land.[4]

Mudskippers[edit]

A mudskipper (Periophthalmus modestus, front).

The mudskippers are fish that spend more time on land than in water with pectoral fins adapted for hopping on land and get their food in the air. Mudskippers can even climb trees; some have suckers on their fins to help them climb. They breathe through their skin and also their gills which are kept moist with water stored in in a specialised organ. Mudskippers mainly return to water to keep their gills moist.[5][6][7]

Climbing perch[edit]

Climbing perch (family Anabantidae) are a diverse group of East Asian and African fish that live in oxygen poor water and are adapted to air breathing, indeed the fish suffocate without access to air. A specialized organ for air exchange called the labyrinth organ has evolved out of modified gill tissue. Climbing perch (not true perch) have varied shapes and some rear their young in a bubble nest that keeps the fry near the surface till the labyrinth organ has developed. Climbing perch come out onto land during rainy weather using their gill covers and fins as limbs and their tails for propulsion. When moving on land then they look for new watery places to live. Like the walking catfish discussed below they survive in a similar way to the Palaeozoic Tiktaalik and like the walking catfish can become invasive.[8][9][10][11][12]

Mangrove rivulus[edit]

The Mangrove rivulus (Kryptolebias marmoratus) is a fish that can live out of water for months at a time breathing air through its skin. This fish is yet another example showing how fish are capable of evolving into land animals. These fish live in mangrove swamps which from time to time dry out. When this happens the fish seek moist, sheltered places like hollow tree logs or leaf litter and stay there till conditions improve. Another odd feature of these fish is that they can reproduce without sex, producing clones of themselves.[13][14][15]

European and American eels[edit]

Eels normally live in water but can travel over land if they need to do this in the course of their migration.[16][17] Out-of-water eels breathe through their skins.[18]

Walking catfish[edit]

The Walking catfish (Clarias batrachus) is yet another fish that can live on land, and like climbing perch it survives in a similar way to the Palaeozoic Tiktaalik. The walking catfish normally lives in the type of water that can dry up, and when this happens the fish moves out onto dry land using its rigid pectoral fins as stilts. Walking catfish literally walk till they find water where they can live. These fish have a specialised air breathing apparatus in their gills. In humid conditions, the walking catfish can survive for hours out of water, and shoals of these fish walking on roads sometimes force motorists to stop driving.[19]

The walking catfish survives and reproduces so effectively that when introduced in the wrong places it can become a pest. There are problems in Florida,[20] and trouble could develop in the UK.[21]

Lungfish[edit]

Top-bottom: South American, African and Australian lungfish.

The lungfish are the closest living relative of tetrapods. They breathe through lungs like our lungs and can survive in brackish water with low oxygen content due to this. When their water dries up lungfish can remain dormant in burrows breathing air for years.

Blue Dwarf Snakehead[edit]

The Blue dwarf snakehead fish (Channa sp.) was recently found in West Bengal, India by the World Wildlife Fund. The Blue Dwarf Snakehead fish has gills, but can also directly breathe air and survive on land for 4 days.[22]

Northern Snakehead[edit]

The Northern Snakehead (Channa argus), native to eastern Asia,[23] is a notorious invasive species in the eastern United States. The slimy predators gulp air and can survive out of water for several days at a time. They're also able to wiggle on land between water sources, although sensationalist media reports have over-dramatized their ability to "walk" on land.[24]

Palaeozoic fish[edit]

Before the fish evolved to become amphibians there were plants and invertebrates on land but nothing needed to evolve defences against vertebrate methods of feeding. Therefore it is likely any fish that could survive in brackish water, in shallow water or on land even for a short time could get plenty of food that was easy to take. This could apply to carnivores or herbivores and could have been a factor in fish evolving to live on land.

See Tiktaalik and Ichthyostega for examples.

Tetrapods[edit]

As it is impossible to define a group from a common ancestor that contains (for example) both coelacanths and lungfishes but not humans, cladistically speaking all tetrapods are fish, and all extant tetrapods can survive on land to some degree (at least in their adult forms), although some aquatic ones like dolphins probably wouldn't last too long without a source of food. Probably the closest living exception is the axolotl,Wikipedia which unlike most amphibians will not metamorphose on its own and will keep its gills for its entire life. Transformation can be forced on them by putting iodine in their water, but it's not recommended as they will not thrive as well as they do in water.[25]

Creationist responses[edit]

All this has proponents of evolution saying "Look! See!" and creationists responding "er… look over there, a Crocoduck!" *flees*

Alternatively, a favoured creationist response is to continually repeat something like, "A fish couldn't possibly survive with half a lung and half a gill"[26][note 1] while ignoring the evidence. Florida, where the walking catfish is a problem, is in the Bible Belt. Therefore, ignoring this evidence could become progressively harder for Bible Belt Christians as the fish spreads – that fish really is a pest.[note 2]

See also[edit]

Notes[edit]

  1. ↑ Even though there are fish with both lungs and gills…
  2. ↑ And not just in the sense of "its existence is inconvenient for creationists", which doesn't really count.

References[edit]

  1. ↑ 1.0 1.1 Slow, cold reptiles may breathe like energetic birds: One-way airflow, thought to exist only in birds, may keep several reptiles going by Susan Milius (1:11pm, October 19, 2015) Science News.
  2. ↑ 2.0 2.1 These fish would rather walk: Slowpokes of the sea, frogfish and handfish barely manage to swim by Susan Milius (8:00am, September 23, 2015) Science News.
  3. ↑ K.P. Dial, N. Shubin and E.L. Brainerd, Eds. Great Transformations in Vertebrate Evolution. University of Chicago Press, 2015. ISBN 022626825X.
  4. ↑ A fish out of water — walks and morphs, Susan Millius, ScienceNews Explores 9 September 2014
  5. ↑ Mudskippers: Walking Fish
  6. ↑ Mudskippers
  7. ↑ Giant Mudskippers
  8. ↑ Climbing perch
  9. ↑ The Labyrinth Fishes
  10. ↑ Anabantidae — Labyrinth Fishes
  11. ↑ The Climbing Perch
  12. ↑ Climbing perch
  13. ↑ BBC Nature: Shells, trees and bottoms — Strange places fish live
  14. ↑ Reuters: Tropical fish can live for months out of water November 15, 2007
  15. ↑ Aalok Mehta, Fish Lives in Logs, Breathing Air, for Months at a Time. Part 1, Part 2. Archived from National Geographic, 6 November 2007.
  16. ↑ European eel
  17. ↑ Common Common eel crossing land
  18. ↑ Eel-tastic
  19. ↑ Walking catfish
  20. ↑ Introduced Species Summary Project
  21. ↑ Walking catfish spotted in the Thames by angler
  22. ↑ John Virata, Blue Dwarf Snakehead Fish Discovered in India. Archived from fishchannel.com, 7 October 2015.
  23. ↑ Northern Snakehead. National Invasive Species Information Center, United States Department of Agriculture.
  24. ↑ Guy Eroh and Katrina Liebich, The Snakehead Dilemma: Considering an Often-Maligned Species. United States Fish and Wildlife Service.
  25. ↑ Axolotls: Meet the amphibians that never grow up, Hayley Dunning, Natural History Museum
  26. ↑ Joachim Vetter, Something fishy about lungs. creation.com.


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