Amphibious fish
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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. These fish use a range of terrestrial locomotory modes, such as lateral undulation, tripod-like walking (using paired fins and tail), and jumping. Many of these locomotory modes incorporate multiple combinations of pectoral, pelvic and tail fin movement. [1]
Many ancient fish had lung-like organs, and a few, such as the lungfish, still do. Some of these ancient "lunged" fish were the ancestors of modern amphibians. However, in most recent fish species these organs evolved into the swim bladders, which help control buoyancy. Having no lung-like organs, modern amphibious fish and also many fish in oxygen poor water, use other methods such as their gills or their skin to breathe air. Amphibious fish may also have eyes adapted to allow them to see clearly in air, despite the density differences between air and water. [2]
[edit] List of amphibious fish
[edit] Lung breathers
- Various "lunged" fish:. These are now extinct. A few of this group were ancestors of the basal tetrapods that led to all tetrapods: amphibians, reptiles, birds, and mammals.
- Lungfish (Dipnoi): Six species, have limb like fins, and can breathe air. Some are obligate air breathers. Some species will bury in the mud when the body of water they live in dries up, surviving up to two years until water returns.
[edit] Gill or skin breathers
- Rockskippers: These are found in Panama. These fish come onto land to catch prey and escape aquatic predators. They often come out of water for up to 20 minutes.
- Wooly sculpin: Found in tide pools along the Pacific coast, these fish will leave water if the oxygen levels get low and can breathe air for 24 hours.
- Mudskippers (Oxudercinae): This subfamily of gobies is probably the most land adapted of fish. Mudskippers are found in mangrove swamps in Africa and the Indo-Pacific, they frequently come onto land and can survive in air for up to three and a half days [3]. Mudskippers breathe through their skin and also through the lining of the mouth (the mucosa) and throat (the pharynx). This requires the mudskipper to be wet, limiting mudskippers to humid habitats. This mode of breathing, similar to that employed by amphibians, is known as cutaneous breathing. They propel themselves over land on their sturdy forefins.
- Anableps: Found in Central and South America, the unusual "four-eyed" and "four-sexed" fish can move on land for short periods of a time. Its pupils are divided into two. The upper half is adapted to see in air, and the lower half is for seeing in water.
- Eels: Some eels, such as the European eel and the American eel, can live for an extended time out of water and can crawl on land if the soil is moist.
- Snakehead fish (Channidae): This family of fish are obligate air breathers, breathing air using their suprabranchial organ, which is a primitive labyrinth organ. The Northern Snakehead has a limited capacity to wriggle over wet grass and mud.
- Airbreathing catfish (Clariidae). This family of fish has a labyrinth organ which allows them to breathe air. Some species from this group can "walk" on land. For example the Walking catfish (Clarias batrachus) of Southeast Asia, can "walk" on land by wriggling and using its pectoral fins, this allows it to move between the slow-moving, and often stagnant and temporary bodies of water in which it lives. Another amphibious species of this family is the Eel catfish (Channallabes apus), which lives in swamps in Africa, and known to hunt beetles on land [4].
- Labyrinth fish (Anabantoidei). This suborder of fish also use also use a labyrinth organ to breathe air. Some species from this group can move on land. An amphibious fish from this family is the Climbing gourami, an African and Southeast Asian fish that is capable of moving from pool to pool over land by using its pectoral fins, caudal peduncle and gill covers as a means of locomotion. It is said that climbing gourami move at night in groups.
