A coenocyte () is a

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 coord ...

cell which can result from multiple nuclear divisions without their accompanying

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 me ...

, in contrast to a

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

, which results from cellular aggregation followed by dissolution of the

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the ...

s inside the mass. The word syncytium in

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

embryology Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos an ...

is used to refer to the coenocytic blastoderm of

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s. A coenocytic colony is referred to as a coenobium (plural coenobia), and most coenobia are composed of a distinct number of cells, often as a multiple of two (4, 8, etc.). Research suggests that coenobium formation may be a defense against grazing in some species.

Physiological examples

Protists

Diplomonad The diplomonads (Greek for "two units") are a group of flagellates, most of which are parasitic. They include '' Giardia duodenalis'', which causes giardiasis in humans. They are placed among the metamonads, and appear to be particularly clo ...

s, like '' Giardia'', have two nuclei.

Ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a differen ...

s have cells that contain two nuclei: a macronucleus and a

micronucleus Micronucleus is the name given to the small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during cell division. It usually is a sign of genotoxic events and chromosomal i ...

. The schizont of apicomplexan

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

s is a form of a coenocyte (i.e. a plasmodium in the general sense) as well as the plasmodia of microsporidian (

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

) and myxosporidian (

Metazoa Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...

) parasites. The trophont of syndinean (Dinoflagellata) parasites.

Xenophyophorea Xenophyophorea is a clade of foraminiferans. Members of this class are multinucleate unicellular organisms found on the ocean floor throughout the world's oceans, at depths of . They are a kind of foraminiferan that extract minerals from th ...

are giant cells with numerous nuclei, and is common on the

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between and . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. ...

Algae

Coenocytic cells are present in diverse and unrelated groups of algae, including

Xanthophyceae Yellow-green algae or the Xanthophyceae (xanthophytes) are an important group of heterokont algae. Most live in fresh water, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamen ...

(e.g., ''Vaucheria''), red algae (e.g., ''Griffithsia'') and

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

(e.g., the internodal cells of '' Chara''). In the siphonous

green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

e Bryopsidales and some Dasycladales the entire thallus is a single multinucleate cell, which can be many meters across (e.g. ''

Caulerpa ''Caulerpa'' is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world. A species in the Mediterr ...

''). However, in some cases, crosswalls may occur during reproduction. The green algal order Cladophorales is characterized by siphonocladous organization, i.e., the thalli are composed of many coenocytic cells. In contrast to the Cladophorales where nuclei are organized in regularly spaced cytoplasmic domains, the cytoplasm of Bryopsidales exhibits streaming, enabling transportation of organelles, transcripts and nutrients across the plant. The

Sphaeropleales Sphaeropleales is an order of green algae that used to be called Chlorococcales. The order includes some of the most common freshwater planktonic algae such as '' Scenedesmus'' and '' Pediastrum''. The Spaeropleales includes vegetatively non-mot ...

also contain several common freshwater species that are coenocytic, namely Scenedesmus, Hydrodictyon, and Pediastrum.

Myxogastrids (slime molds)

:''See Plasmodium (life cycle).''

Plants

The

endosperm The endosperm is a tissue produced inside the seeds of most of the flowering plants following double fertilization. It is triploid (meaning three chromosome sets per nucleus) in most species, which may be auxin-driven. It surrounds the embryo an ...

plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

begins to grow when one fertilized cell (the primary endosperm cell) becomes a coenocyte. Different species produce coenocytes with different numbers of nuclei before the PEC eventually begins to subdivide, with some growing to contain thousands of nuclei.

Fungi

Some filamentous fungi (Such as Glomeromycota, Chytridiomycota and Neocalligomastigomycota) may contain multiple nuclei in a coenocytic

mycelium Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates in ...

. A coenocyte functions as a single coordinated unit composed of multiple cells linked structurally and functionally, i.e. through gap junctions. Fungal mycelia in which

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e lack

septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates transit bus, bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people ...

are known as "aseptate" or "coenocytic".

Metazoans: invertebrates

Many insects, such as the model organism ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the " vinegar fly" or " pomace fly". Starting with ...

'', lay eggs that initially develop as "syncytial" blastoderms, i.e. early on the

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

s exhibit incomplete

cell division Cell division is the process by which a parent cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there ar ...

. The nuclei undergo S-phase (DNA replication) and sister chromatids get pulled apart and re-assembled into nuclei containing full sets of homologous chromosomes, but

does not occur. Thus, the nuclei multiply in a common cytoplasmic space. The early embryo "syncytium" of invertebrates such as ''Drosophila'' is important for "syncytial" specification of cell differentiation. The egg cell cytoplasm contains localized

mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the ...

molecules such as those that encode the

transcription factors In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...

Bicoid and Nanos. Bicoid protein is expressed in a gradient that extends from the anterior end of the early embryo, whereas Nanos protein is concentrated at the posterior end. At first, the nuclei of the early embryo rapidly and synchronously divide in the "syncytial" blastoderm and then migrate through the cytoplasm and position themselves in a monolayer around the periphery, leaving only a small number of nuclei in the center of the egg, which will become yolk nuclei. The position of the nuclei along the embryonic axes determines the relative exposure of different amounts of Bicoid, Nanos, and other morphogens. Those nuclei with more Bicoid will activate genes that promote differentiation of cells into head and thorax structures. Nuclei exposed to more Nanos will activate genes responsible for differentiation of posterior regions, such as the abdomen and

germ cells Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embry ...

. The same principles hold true for the specification of the dorso-ventral axis – higher concentration of nuclear Dorsal protein on the ventral side of the egg specify the ventral fate, whereas absence thereof allows dorsal fates. After the nuclei are positioned in a monolayer underneath the egg membrane, the membrane begins to slowly invaginate, thus separating the nuclei into cellular compartments; during this period, the egg is called a cellular blastoderm. The pole cells – the germline anlage – are the first cells to separate fully.

Pathological examples

Certain mutations and the activation of certain cell-cycle control genes can lead to bacteria forming "filament-like" cells with multiple chromosomes but without cellular division. These mechanisms or mistakes may lead to a similar structure to a coenocyte, though bacteria do not possess nuclei. This fact has been used in certain synthetic biology applications, for example, to create cell-derived fibers for an organically grown concrete.

Etymology

As with much

international scientific vocabulary International scientific vocabulary (ISV) comprises scientific and specialized words whose language of origin may or may not be certain, but which are in current use in several modern languages (that is, translingually, whether in naturalized, lo ...

, English got the word ''coenocyte'' (''cœnocyte'') from

New Latin New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...

, in which its combining forms, '' coeno-'' + '' -cyte'', are based on ancient

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

: κοινός (''koinós'') = "common" + κύτος (''kýtos'') = "box, i.e. cell"). The stressed vowel is œ, which in scientific English usually sounds like

long e In linguistics, vowel length is the perceived length of a vowel sound: the corresponding physical measurement is length (phonetics), duration. In some languages vowel length is an important phonemic factor, meaning vowel length can change the me ...

and usually shifts a preceding ''c'' to be soft; this explains how there is a degree of regularity in "how one gets a "see-no" sound from ''coeno-''," which might seem irregular at first glance.

References

{{reflist

External links

* http://www.ige.tohoku.ac.jp/outou/outou-e/ceonocytes-e.html Cells Fungal morphology and anatomy