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 of this group is called the "giant amoeba," with the scientific name Chaos carolinense. These organisms can grow up to 5 mm long, though 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 using special methods 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, such as bacteria, algae, other tiny organisms, and even small animals without a backbone. They eat by surrounding their food with parts of their body called pseudopods, forming a ball around the food where it gets broken down by special substances inside the cell. These organisms do not have a mouth or a special spot on their surface for eating.

Movement

The cell’s outer layer, called the plasmalemma, is very flexible, letting 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 similar tiny creatures, Chaos moves by stretching out parts called pseudopodia. When it stretches, a stream of the inner fluid flows inside, helping it move forward. Scientists have written a lot about how this movement works.

Early history and naming controversy

The group of tiny creatures called Chaos has a long and confusing history. In 1755, a scientist named Rösel saw one of these creatures 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 very hard to know which names really 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, which is different from the modern Chaos.

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 very 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 to follow the rules of naming tiny creatures. 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, as suggested by Robert L. King and Theodore L. Jahn in 1948.

Recent phylogeny

The genus Chaos used to be grouped with other similar organisms under the name Sarcodina. But new studies using a special kind of DNA called ribosomal DNA show that Sarcodina actually includes many different groups that are not closely related. Because of this, scientists have split these organisms 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.