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Arcellinida

Adapted from Wikipedia · Discoverer experience

Microscopic shell of Netzelia corona, a single-celled organism called a testate amoeba.

Arcellinid testate amoebae, also known as Arcellinida, Arcellacean, or lobose testate amoebae, are tiny, single-celled creatures called protists. They are special because they live inside a simple shell called a test. These interesting organisms can be found in many places, such as soils, leaf litter, peat bogs, and near or in fresh water.

Arcellinid testate amoebae move and capture food using their pseudopodia, which are temporary extensions of their cells. Most scientists think they reproduce asexually by splitting into two parts, a process called binary fission. But new research suggests that these creatures might actually recombine genetically in a way similar to sexual reproduction more often than we used to believe, especially for amoeboid protists like them.

Morphology

Arcellinida always have a shell, called a test, that sits outside their cell membrane. These shells are made from organic or mineral materials, either secreted by the organism or gathered from outside particles. The test has one main opening.

These shells can help scientists understand past environmental changes. By studying the composition of old shells, researchers can learn about past climate change and water conditions during the Holocene. Different species of testate amoebae prefer specific environments, which makes them useful for reconstructing past conditions.

Evolutionary history

Fossils of these tiny creatures go back to a time called the Tonian stage of the Proterozoic, about 789 to 759 million years ago. By 730 million years ago, they had already developed into many different types.

Scientists think these creatures might have come from more than one ancient ancestor, but one group called testaceafilosea likely came from a single ancestor. Their old shells are often found in fossilized amber, and some have been found in very old lake sediments. It seems they have changed very little over the past many millions of years.

Classification

The Arcellinida are a group of single-celled organisms that live in places like soil, leaf litter, peat bogs, and near fresh water. They have a simple shell called a "test" and use temporary extensions of their body called pseudopodia to move and eat.

The Arcellinida are grouped into several suborders and families, including:

Related articles

Asexual reproduction
Holocene
Tonian
Proterozoic

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