Now, coelacanths are pretty spectacular as they pre-date dinosaurs (the Devonian Period- i.e. `the Age of Fishes,' 360 million years ago) and are still around today, with little to no alterations.
There's a widely accepted scientific belief that life on Earth started in the ocean. There's an interesting story about how two curious scientists tested this belief - Miller/Urey. They set up an experiment to simulate how the Earth may have started to react at the beginning - at first the Earth didn't have any water in it, only hydrogen, oxygen, nitrogen, methane, and ammonia. It was a rocky surface, and was extremely hot - water only existed in the atmosphere as gas molecules. One billion years later it started to cool, and the water condensed - precipitation occurred. Chemical weathering occurred thereafter, and soluble minerals dissolved salts, and began collecting in the lower portions of the rocky bed. Water is so important in any system - the molecules formed after the gases reacted with one another, diffused, and were free to move. These first molecules were DNA and enzymes (must need both) - and co-evolved. Even though silica is most abundant, we are based on carbon! After the experiment, the substance collected was then taken back to a laboratory to be examined (through chromotography) - later it was found that the substance did contain the elements of life - amino acids (which are used to make proteins).
Evolution relates to change (in life), and `to evolve' basically means `to change'. Coelacanths are lobe-finned fish (a group of bony fishes with paired founded fins, suggesting limbs) - it uses these to `perch' on the bottom of the ocean. Coelacanths in an isolated area (an area that didn't affect the rest of the species) may have been subject to random mutations (variation) - environmental factors killed those who did not have the mutations required to survive. Those that had the variation in the population survived and continued to breed (forming a new species) - amphibians (an animal capable of living both on land and in water).
In the 1930s coelacanths were thought to be the direct ancestors of the tetrapods (land-living animals - humans included!) Now though, close relatives called `lungfishes' are believed to have been the direct ancestors. Unlike normal fishes with their swim bladder near the dorsal portion of body cavity, lungfishes have swim bladders that open into the lower side of the foregut. To aquire oxygen, they swim up the surface and swallow air into their swim bladder. Up to 95% of their respiratory oxygen may be acquired in this manner. This means that they do not need to swim to attain oxygen, like normal fish. Their 'lungs' were probably not fully functional at this stage, but an air-gulping mechanism that allowed at least some air breathing. In later species, they could drown if they didn't gulp air.
Coelacanths are heavy-armored fish (a reason for their survival). It is the only living animal to have a fully functional intercranial joint (a division, which separates the ear and brain from the nasal organs and eye - it allows the front part of the head to be lifted when the fish is feeding). Probably the most interesting feature about them would be their `paired fins' which move in a similar fashion to our arms and legs. The original coelacanths were cobalt blue, whereas the more-recent ones are reported to be brownish in colour - caused by pollution.
Coelacanths, unlike most other fish, do not lay eggs. Instead, they give birth to live young (called `pups'). They also have an amphibian-like internal system, which offers further suggestion that amphibians evolved from them. The fish is an opportunist predator (meaning it takes every chance it can to get food). It has an uncanny sense of timing and navigational skills yet to be explained. They are also thought to be long lived, though its exact life-span is still unknown. It has a vertebra (a backbone), and even though they lived primarily in saltwater, the lobe-fins are believed to have evolved in freshwater.
Scientists believed that this species was extinct about 90 million years ago, and it was not until 1938 that a living specimen was discovered by thirty two-year-old, Marjorie Courtenay Latimer. These ancient fishes are vital (and living) evidence to support the theory of evolution, and provide the once `missing' link from fish to amphibians. It is to the utmost importance that we conserve and protect these creatures, for everyone's benefit.
General - http://www.dinofish.com/
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Detailed Description - http://expage.com/page/coelecanth
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