arcellinids

Arcellinids are a group of single-celled organisms belonging to the phylum Arcellinida. They are a type of amoeba, characterized by the presence of a shell, also known as a testa. These shells are typically made of organic material, often incorporating mineral particles such as sand grains or iron compounds. Arcellinids are found in a wide variety of freshwater environments, including lakes, ponds, streams, and bogs, as well as in some damp terrestrial habitats.

The shell of an arcellinid provides protection and support for the amoeba. It is usually dome-shaped or ovoid and has a single opening through which the organism can extend its pseudopods. Pseudopods are temporary projections of the cytoplasm that arcellinids use for locomotion and for capturing food. Their diet consists primarily of bacteria, algae, and smaller protists. Reproduction in arcellinids is asexual, typically through binary fission, where one cell divides into two identical daughter cells.

Due to their widespread distribution and the presence of their shells in sediment cores, arcellinids are often used as bioindicators in paleoecological studies. The types and abundance of arcellinid species present in ancient sediments can provide valuable information about past environmental conditions, such as water chemistry, pH, and temperature. Their distinctive shells make them relatively easy to identify and study.