Chaos (genus)

Chaos is a group of tiny, single-celled creatures called amoeboid organisms. They belong to a family known as Amoebidae. The most famous member is called the "giant amoeba," with the scientific name Chaos carolinense. These organisms can grow up to 5 mm long, but most are between 1 and 3 mm.

These creatures look very similar to another group called Amoeba. Both have many long, rounded arms called pseudopods that they use to move and catch food. But there is a big difference! While Amoeba have just one nucleus, Chaos can have as many as a thousand. Because of this, C. carolinense used to be grouped with another giant organism called Pelomyxa palustris.

Recent studies have shown that Chaos is actually more closely related to Amoeba than to Pelomyxa. Now, scientists recognize Chaos as its own special group, closely related to Amoeba.

Dietary habits

Chaos species can eat many different things, like bacteria, algae, other tiny organisms, and small animals without a backbone. They catch their food by using parts of their body called pseudopods, which wrap around the food. The food is then broken down by special substances inside the cell. These organisms do not have a mouth or a special place to eat.

Movement

The cell’s outer layer, called the plasmalemma, is flexible. This lets the organism change shape quickly. Inside, there are two parts: a fluid middle with food and important parts of the cell, and a thicker outer part that is clear.

Like other tiny creatures, Chaos moves by stretching out parts called pseudopodia. When it stretches, fluid from the inside flows in, helping it move forward. Scientists have studied this movement a lot.

Early history and naming controversy

The tiny creatures called Chaos have a long and confusing history. In 1755, a scientist named Rösel saw one and called it "der kleine Proteus" ("the little Proteus"). Later, another scientist named Linnaeus gave it the name Volvox chaos, but changed it to Chaos chaos because the name Volvox was already used for a different group of tiny plants.

As more scientists studied these creatures, they gave them many different names, making it hard to know which names belonged to which group. In 1879, a scientist named Joseph Leidy suggested calling all the large, common water amoebae Amoeba proteus. But he described these as having only one nucleus.

In 1900, a biologist named H. V. Wilson found a very large amoeba with many nuclei in its cells. He placed it in a group called Pelomyxa, naming it Pelomyxa carolinensis. This amoeba became popular for scientists to study in labs.

In 1926, a scientist named Asa A. Schaeffer said that Pelomyxa carolinensis was actually the same as the creature Rösel had seen in 1755. He suggested calling it Chaos chaos. Some scientists agreed, while others did not. By the 1970s, scientists realized there were big differences between this amoeba and others in the Pelomyxa group. Today, it is most commonly called Chaos carolinensis.

Recent phylogeny

The genus Chaos used to be grouped with other similar tiny creatures under the name Sarcodina. But new studies using a special kind of DNA called ribosomal DNA show that Sarcodina includes many different groups that are not closely related. Because of this, scientists have split these creatures into two new larger groups, called Rhizaria and Amoebozoa. Today, Chaos and its close relative, Amoeba, are placed in Amoebozoa. These are simple, single-celled creatures without a hard shell, moving around using parts called pseudopods.

We know that Chaos and Amoeba are very similar, but scientists are still learning more about how these groups are related. Some research suggests that one type of Chaos called Chaos nobile might be an early branch in the family tree, separate from another type called Chaos carolinense and a few species of Amoeba.