You can take a fish out of water.You can take a fish out of water From dinosaurs to dogs, all land vertebrates trace their ancestry back to the water. Sometime around 350 million years ago, fish-like amphibians amphibians members of the animal class Amphibia. Includes frogs, toads, newts, salamanders and cecilians all capable of living on land or in water. crawled out of the water and established for the first time a foothold, or perhaps a fin-hold, on terra firma. While paleontologists believe these amphibians evolved from some primitive fish that had developed the ability to breathe air, they have debated for years which kind or kinds of fish spawned the earliest amphibians. Most theories have held that the ancestral fish must have had special organs, such as lungs, to help them breathe air directly. Yet a new study suggests this argument may not hold water. Physiologist Karen Martin reports that some modern fish lacking special organs can breathe air quite well. Martin, of the University of California, Los Angeles UCLA comprises the College of Letters and Science (the primary undergraduate college), seven professional schools, and five professional Health Science schools. Since 2001, UCLA has enrolled over 33,000 total students, and that number is steadily rising. , placed different near-shore marine fish in a dry chamber and passed air over them while measuring the levels of oxygen and carbon dioxide in air leaving the chamber. She found that for up to an hour, many types, including sculpin sculpin, common name for a member of the large family Cottidae, bizarre fishes with large, spiny or armored heads and short, tapering bodies, found in both marine and freshwater habitats. The family includes the muddlers and some species called bullheads. and a form of toadfish toadfish, common name for the sluggish, bottom-feeding fishes of the genus Opsanus, found in the shallow waters from New Jersey to the Caribbean. Toadfishes feed almost entirely on crustaceans and small fishes. , called midshipman midshipman: see toadfish. , could pull in oxygen and discharge carbon dioxide -- the two key elements of respiration. Modern lungfish lungfish, common name for any of a group of fish belonging to the families Ceratodontidae and Lepidosirenidae, found in the rivers of South America, Africa, and Australia. Like the lobefins, the lungfishes are ancestrally related to the four-footed land animals. and certain fish with gas bladders are well known for their ability to breathe air, but the sculpin and toadfish apparently use the tissue in their gills or mouths to respire re·spire v. 1. To breathe in and out; inhale and exhale. 2. To undergo the metabolic process of respiration. 3. To breathe easily again, as after a period of exertion. , according to Martin. She chose to test these fish because they are found in tidal pools or lagoons, a logical place to look for fish that might be able to breathe, she says. During the day, when tides drop and the sun warms these shallow areas, levels of dissolved oxygen can fall drastically, making it more difficult for fish to absorbe oxygen from the water. Martin's findings do not reveal which ancient fish actually evolved into amphibians, but it opens up the possibilities in the search, she says. Air breathing does not seem to be a unique adaptation, and amphibians may have evolved from fish that lacked special breathing organs. |
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