page_title: Symbiodinium
section_title: Morphology
hierarchical_section_title: Symbiodinium / Morphology
caption_attribution_description: English: Fine scale features and organelles found among Symbiodinium. (A) Close-up of divided cells of a tetrad from a culture of “S. corculorum” that is genetically similar to S. pilosum (both are type A2). This particular lineage is unusual among described Symbiodinium by possessing mucocysts, and chloroplasts with parallel and peripheral thylakoid arrangements. Flagella are seen in cross section in the space between daughter cells. (B) A thick cellulosic cell wall is observed for many cultured isolates. (C) TEM of a cross-section through a chloroplast lobe at the periphery of the cell with parallel and peripheral thylakoids grouped in sets of three.
context_page_description: Symbiodinium is a genus of dinoflagellates that encompasses the largest and most prevalent group of endosymbiotic dinoflagellates known. These unicellular algae commonly reside in the endoderm of tropical cnidarians such as corals, sea anemones, and jellyfish, where the products of their photosynthetic processing are exchanged in the host for inorganic molecules. They are also harbored by various species of demosponges, flatworms, mollusks such as the giant clams, foraminifera, and some ciliates. Generally, these dinoflagellates enter the host cell through phagocytosis, persist as intracellular symbionts, reproduce, and disperse to the environment. The exception is in most mollusks, where these symbionts are intercellular. Cnidarians that are associated with Symbiodinium occur mostly in warm oligotrophic, marine environments where they are often the dominant constituents of benthic communities. These dinoflagellates are therefore among the most abundant eukaryotic microbes found in coral reef ecosystems.
  Symbiodinium are colloquially called zooxanthellae, and animals symbiotic with algae in this genus are said to be "zooxanthellate".
context_section_description: The morphological description of the genus Symbiodinium is originally based on the type species (holotype) Symbiodinium microadriaticum. Because these dinoflagellates possess two major stages in their life history (see above), namely the mastigote (motile) and coccoid (non-motile) stages, the morphology of both is described in order to provide a complete diagnosis of the organism.
caption: Fine scale features and organelles found among Symbiodinium. (A) Close-up of divided cells of a tetrad from a culture of “S. corculorum” that is genetically similar to S. pilosum (both are type A2). This particular lineage is unusual among described Symbiodinium by possessing mucocysts, and chloroplasts with parallel and peripheral thylakoid arrangements. Flagella are seen in cross section in the space between daughter cells.  (B) A thick cellulosic cell wall is observed for many cultured isolates. (C) TEM of a cross-section through a chloroplast lobe at the periphery of the cell with parallel and peripheral thylakoids grouped in sets of three.
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