A coenocyte () is a

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

cell which can result from multiple nuclear divisions without their accompanying

cytokinesis Cytokinesis () is the part of the cell division process and part of mitosis 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 contrast to a

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

, which results from cellular aggregation followed by dissolution of the

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

s inside the mass. The word syncytium in

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

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

is used to refer to the coenocytic blastoderm of

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s. A coenocytic colony is referred to as a coenobium (: 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 close ...

s, like ''

Giardia ''Giardia'' ( or ) is a genus of anaerobic flagellated protozoan parasites of the phylum Metamonada that colonise and reproduce in the small intestines of several vertebrates, causing the disease giardiasis. Their life cycle alternates be ...

'', 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 flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

s have cells that contain two nuclei: a

macronucleus A macronucleus (formerly also meganucleus) is the larger type of nucleus in ciliates. Macronuclei are polyploid and undergo direct division without mitosis. It controls the non-reproductive cell functions, such as metabolism Metabolism (, ...

and a micronucleus. The

schizont Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism ...

apicomplexa The Apicomplexa (also called Apicomplexia; single: apicomplexan) are organisms of a large phylum of mainly parasitic alveolates. Most possess a unique form of organelle structure that comprises a type of non-photosynthetic plastid called an ap ...

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

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

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.Franzen, C. (2005). How do Microsporidia inva ...

n (

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

) and myxosporidian (

Metazoa Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hol ...

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

Xenophyophorea Xenophyophorea is a clade of foraminiferans. Xenophyophores 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 their surround ...

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 . 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. They ...

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 Red algae, or Rhodophyta (, ; ), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest Phylum, phyla of algae, containing over 7,000 recognized species within over 900 Genus, genera amidst ongoing taxon ...

(e.g., ''Griffithsia'') and

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

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

green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...

Bryopsidales Bryopsidales is an order of green algae, in the class Ulvophyceae. It is a diverse group of mostly marine macroalgae. Characteristics The thallus is filamentous, highly branched, and may be packed into a mass. It is coenocytic, having multi-nu ...

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 cell nucleus, nuclei, making them among the biggest single cells in the world. Referring to ...

''). However, in some cases, crosswalls may occur during reproduction. The green algal order Cladophorales is characterized by siphonocladous organization, i.e., the

thalli Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

are composed of many coenocytic cells. In contrast to the Cladophorales where nuclei are organized in regularly spaced cytoplasmic domains, the cytoplasm of

exhibits streaming, enabling transportation of organelles, transcripts and nutrients across the plant. The Sphaeropleales also contain many common freshwater genera that are coenocytic, such as '' Scenedesmus'', '' Hydrodictyon'', and '' Pediastrum''.

Myxogastrids (slime molds)

:''See

Plasmodium (life cycle) A plasmodium is a living structure of cytoplasm that contains many nuclei, rather than being divided into individual cells each with a single nucleus. Plasmodia are best known from slime molds, but are also found in parasitic Myxosporea, and s ...

.''

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#Pla ...

plants Plants are the eukaryotes that form the kingdom Plantae; they are predominantly photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars f ...

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 (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...

. 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 SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

are known as "aseptate" or "coenocytic".

Metazoans: invertebrates

Many insects, such as the model organism ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), 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", "pomace fly" ...

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

embryo An embryo ( ) is the initial stage of development for 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 sp ...

s exhibit incomplete

cell division Cell division is the process by which a parent cell (biology), 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 eukar ...

. The nuclei undergo

S-phase S phase (Synthesis phase) is the phase of the cell cycle in which DNA is DNA replication, replicated, occurring between G1 phase, G1 phase and G2 phase, G2 phase. Since accurate duplication of the genome is critical to successful cell division, ...

(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 Protein biosynthesis, synthesizing a protein. mRNA is ...

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 fun ...

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 A morphogen is a substance whose non-uniform distribution governs the Natural patterns, pattern of tissue development in the process of morphogenesis or pattern formation, one of the core processes of developmental biology, establishing positio ...

. 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 A germ cell is any cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo ...

. 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

Neo-Latin Neo-LatinSidwell, Keith ''Classical Latin-Medieval Latin-Neo Latin'' in ; others, throughout. (also known as New Latin and Modern Latin) is the style of written Latin used in original literary, scholarly, and scientific works, first in Italy d ...

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

Greek Greek may refer to: 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 of all kno ...

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

External links

* {{cite web , url=http://www.ige.tohoku.ac.jp/outou/outou-e/ceonocytes-e.html , title=無節藻の生物学と多核細胞研究会 Cells Fungal morphology and anatomy