![Hemitrichia serpula 57955](https://upload.wikimedia.org/wikipedia/commons/1/1d/Hemitrichia_serpula_57955.jpg)
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. The ...
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 mu ...
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 bryozoan) ...
, and some algae such as the
Chlorarachniophyta.
Structure
A plasmodium is an
amoeboid
An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
,
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 coordinat ...
, and naked mass 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. The ...
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, respectively ...
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 insid ...
, 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 meios ...
, 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 nucleus) ...
, 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
, usually refers to the feeding stage of
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 mu ...
s; these are macroscopic
mycetozoa
Mycetozoa is a polyphyletic grouping of slime molds. It was originally thought to be a monophyletic clade, but recently it was discovered that protostelia are a polyphyletic group within Conosa.
Classification
It can be divided into dictyostelid ...
ns.
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 para ...
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 prot ...
(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 from ...
) and
Myxosporidia
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 bryozoan) ...
(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 th ...
), former
cnidospora Cnidospora is a wikt:Defunct, defunct subphylum of microscopic spore-forming parasites in the defunct phylum Protozoa. The subphylum was divided into two class (biology), classes, the Myxosporea, Myxosporidea (now classified as higher-animals, i.e. ...
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 foramini ...
, 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 enzy ...
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 eu ...
n algae, e.g.
Chlorarachniophyta, are called plasmodia. These lack cell walls; the
syncytia
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 nucleus) ...
are created by cell fusion. Some
plasmodiophorid
The Phytomyxea are a class of parasites that are cosmopolitan, obligate biotrophic protist parasites of plants, diatoms, oomycetes and brown algae. They are divided into the orders Plasmodiophorida ( ICZN, or Plasmodiophoromycota, ICBN) and Ph ...
s and
haplosporid
The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecul ...
ians 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