Marine Biology

The Life Cycle of the American Eel Anguilla Rostrata



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The never ending controversies surrounding Darwin’s Theory of Evolution comes to mind when learning the life cycle of the American Eel. The theory is that over hundreds of millions of years, humans evolved from fish that crawled out of the ocean on four limbs (tetrapods) and breathed air through lungs. Studying the life cycle of Anquilla rostrata makes the theory of evolution more plausible. The American Eel can crawl over land obstacles and can breathe air because their skin can absorb oxygen for several hours. The American Eel also has an unusual life cycle which could point to evolution. Is it possible that Anguilla rostrata is an ancient relative of man?

Eels are some of the most fascinating and mysterious of sea creatures.  While eels may resemble land snakes, they are not snakes at all. Eels, or Anguilloformes, are fish. Anquilla Rostrata is the American Eel and is called Kat because it is a catadromous fish.  A catadromous fish is unusual in that, unlike most fish, it spawns in oceans but spends most of its life in fresh water.

Another difference is that most fish grow throughout their lives; Kat grows to maturity quickly, spawns, and then dies. The actual birthplace of this fish is unknown, but larvae are found in the Sargasso Sea, which is near the Bahamas in the area known as the Bermuda Triangle. Kat’s life begins between January and March as a transparent larva. Its shape resembles a willow leaf. For a year, they feed on plankton then develop into a glass transparent eel.

During this year, Kat travels through the Gulf Stream to the coast of North America.  Upon entering fresh water, Kat turns yellow in color for a few years. Kat swims to freshwater rivers and streams. They can also swim in underground waterways and end up in ponds without streams. As it travels, Kat has the ability to overcome obstacles such as rocks and dams. Kat can climb over these obstacles. Kat can survive out of water for several hours because its skin can absorb oxygen allowing them to breathe.

When they reach fresh water they begin a metamorphasis in appearance and shape. They become darker and rounder. They are now called “elvers” until they mature. Maturity takes three years and they can grow up to five feet in length. Because maturity is prolonged, Kat is vulnerable to fisheries, and water contaminants. At maturity, Kat is covered with a mucous layer that makes it feel slimy. A low fin runs down the middle of its back.

The American eel may live up to thirty years or longer in fresh water before returning to the Sargasso Sea to spawn. After spawning they die.  A Kat that was captured as an “Elfer” lived in an Aquarium for eighty five years.

Eels are important to our ecosystem because they eat mosquitoes and other fish, thus helping control those populations. They also eat dead matter that other animals will not eat.  But Kat may be in danger, because they, themselves, are eaten by many people, mostly Europeans and Asians. Recipes for the American Eel include Jellied Eel, Eel Escabeche, and Eel in Green Sauce and Stir Fried Eel. Kat is also vulnerable to fisheries and water contaminants. 

The American Eel is a fascinating fish that may hold secrets to the beginning of life. It has an unusual life cycle, and has the ability to overcome physical obstacles on earth by climbing. It is unusual in that it can survive for hours outside of water because its skin can absorb oxygen. It is eaten by many people thus helping feed the population. They are harmless and help keep American waterways clean and healthy.


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ARTICLE SOURCES AND CITATIONS
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