A plasmodium is a living structure of

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

that contains many nuclei, rather than being divided into individual cells each with a single nucleus. Plasmodia are best known from

slime mold Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mul ...

s, but are also found in parasitic

Myxosporea Myxosporea is a class of microscopic parasites, belonging to the Myxozoa clade within Cnidaria. They have a complex life cycle which comprises vegetative forms in two hosts, an aquatic invertebrate (generally an annelid but sometimes a bryozoa ...

, and some algae such as the

Chlorarachniophyta The chlorarachniophytes are a small group of exclusively marine algae widely distributed in tropical and temperate waters. They are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. Normally the ...

Structure

A plasmodium is an amoeboid,

multinucleate Multinucleate cells (also known as multinucleated or polynuclear cells) are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordina ...

, and naked mass of

that contains many

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectiv ...

nuclei. The resulting structure, a

coenocyte A coenocyte () is a multinucleate cell which can result from multiple nuclear divisions without their accompanying cytokinesis, in contrast to a syncytium, which results from cellular aggregation followed by dissolution of the cell membranes insi ...

, is created by many nuclear divisions without the process of

cytokinesis Cytokinesis () is the part of the cell division process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division in mitosis and mei ...

, which in other organisms pulls newlydivided cells apart. In some cases, the resulting structure is a

syncytium A syncytium (; plural syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell which can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleu ...

, created by the fusion of cells after division. Under suitable conditions, plasmodia differentiates and forms fruiting bodies bearing spores at their tips.

Taxonomic distribution

The term plasmodium, introduced by Leon Cienkowski, usually refers to the feeding stage of

s; these are macroscopic mycetozoans. The multinucleate developmental stages of some

intracellular parasite Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. Types of parasites There are two main types of intracellular parasites: Facultative and Obligate. Facultative intracellular pa ...

s, namely

Microsporidia Microsporidia are a group of spore-forming unicellular parasites. These spores contain an extrusion apparatus that has a coiled polar tube ending in an anchoring disc at the apical part of the spore. They were once considered protozoans or pr ...

(now in

Fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

) and Myxosporidia (now in

Cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that ...

), former

cnidospora Cnidospora is a defunct subphylum of microscopic spore-forming parasites in the defunct phylum Protozoa. The subphylum was divided into two classes, the Myxosporidea (now classified as higher-animals, i.e. Metazoa) and the Microsporidea (now cla ...

ns, are also sometimes called plasmodia.Hoek, C. van den, Mann, D.G. and Jahns, H.M. (1995). Algae An Introduction to Phycology. Cambridge University Press, Cambridge. . Similarly, in

Rhizaria The Rhizaria are an ill-defined but species-rich supergroup of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthethic, but many forami ...

, the amoeboid, multinucleate

protoplast Protoplast (), is a biological term coined by Hanstein in 1880 to refer to the entire cell, excluding the cell wall. Protoplasts can be generated by stripping the cell wall from plant, bacterial, or fungal cells by mechanical, chemical or e ...

s of some

Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major euk ...

n algae, e.g.

, are called plasmodia. These lack cell walls; the syncytia are created by cell fusion. Some plasmodiophorids and haplosporidians are other multinucleated rhizarians.Brown MW, Kolisko M, Silberman JD, Roger AJ. (2012)
Aggregative Multicellularity Evolved Independently in the Eukaryotic Supergroup Rhizaria
''Current Biology'', Volume 22, Issue 12, 1123-1127.

References

{{Authority control SAR supergroup biology