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A coenocyte () is a multinucleate cell which can result from multiple karyokinesis without their accompanying cytokinesis, in contrast to a syncytium, which results from cellular aggregation followed by dissolution of the inside the mass. The word syncytium in animal embryology is used to refer to the coenocytic blastoderm of . 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.
have cells that contain two nuclei: a macronucleus and a micronucleus.
The schizont of is a form of a coenocyte (i.e. a plasmodium in the general sense) as well as the plasmodia of (Fungi) and (Metazoa) parasites.
The trophozoite of (Dinoflagellata) parasites.
Xenophyophorea are giant cells with numerous nuclei, and is common on the .
In the siphonous Bryopsidales and some Dasycladales, the entire thallus is a single multinucleate cell, which can be many meters across (e.g. Caulerpa). However, in some cases, crosswalls may occur during reproduction.
The green algal order Cladophorales is characterized by siphonocladous organization, i.e., the thallus 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 also contain many common freshwater genera that are coenocytic, such as Scenedesmus, Hydrodictyon, and Pediastrum.
The early embryo "syncytium" of invertebrates such as Drosophila is important for "syncytial" specification of cell differentiation. The egg cell cytoplasm contains localized mRNA molecules such as those that encode the transcription factors Morphogenesis 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. 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 – the germline anlage – are the first cells to separate fully.
This fact has been used in certain synthetic biology applications, for example, to create cell-derived fibers for an organically grown concrete.
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